                             COUR INTERNATIONALE DE JUSTICE

                                RECUEIL DES ARRÊTS,
                         AVIS CONSULTATIFS ET ORDONNANCES

              CERTAINES ACTIVITÉS MENÉES PAR LE NICARAGUA
                      DANS LA RÉGION FRONTALIÈRE
                              (COSTA RICA c. NICARAGUA)

                                           et

                    CONSTRUCTION D’UNE ROUTE AU COSTA RICA
                          LE LONG DU FLEUVE SAN JUAN
                              (NICARAGUA c. COSTA RICA)

                             ARRÊT DU 16 DÉCEMBRE 2015

                                    2015
                             INTERNATIONAL COURT OF JUSTICE

                              REPORTS OF JUDGMENTS,
                           ADVISORY OPINIONS AND ORDERS

               CERTAIN ACTIVITIES CARRIED OUT BY NICARAGUA
                           IN THE BORDER AREA
                              (COSTA RICA v. NICARAGUA)

                                          and

                     CONSTRUCTION OF A ROAD IN COSTA RICA
                          ALONG THE SAN JUAN RIVER
                              (NICARAGUA v. COSTA RICA)

                            JUDGMENT OF 16 DECEMBER 2015

5 Ord 1088.indb 1                                             19/10/16 12:01

                                              Mode officiel de citation :
                       Certaines activités menées par le Nicaragua dans la région frontalière
                       (Costa Rica c. Nicaragua) et Construction d’une route au Costa Rica
                              le long du fleuve San Juan (Nicaragua c. Costa Rica),
                                          arrêt, C.I.J. Recueil 2015, p. 665

                                                 Official citation :
                         Certain Activities Carried Out by Nicaragua in the Border Area
                       (Costa Rica v. Nicaragua) and Construction of a Road in Costa Rica
                              along the San Juan River (Nicaragua v. Costa Rica),
                                      Judgment, I.C.J. Reports 2015, p. 665

                                                                                1088
                                                                  No de vente:
                    ISSN 0074-4441                                Sales number
                    ISBN 978-92-1-157280-3

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                                                     16 DÉCEMBRE 2015

                                                           ARRÊT

                    CERTAINES ACTIVITÉS MENÉES PAR LE NICARAGUA
                            DANS LA RÉGION FRONTALIÈRE
                             (COSTA RICA c. NICARAGUA)
                                        et
                      CONSTRUCTION D’UNE ROUTE AU COSTA RICA
                            LE LONG DU FLEUVE SAN JUAN
                             (NICARAGUA c. COSTA RICA)

                    CERTAIN ACTIVITIES CARRIED OUT BY NICARAGUA
                                IN THE BORDER AREA
                             (COSTA RICA v. NICARAGUA)
                                        and
                       CONSTRUCTION OF A ROAD IN COSTA RICA
                            ALONG THE SAN JUAN RIVER
                             (NICARAGUA v. COSTA RICA)

                                                    16 DECEMBER 2015

                                                         JUDGMENT

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                                                                                665

                                            TABLE OF CONTENTS

                                                                                Paragraphs

                    Chronology of the Procedure 	                                             1‑52
                     I. Jurisdiction of the Court	                                           54‑55
                    II. Geographical and Historical Context and Origin of the
                        Disputes 	                                                           56‑64
                    III. Issues in the Costa Rica v. Nicaragua Case 	                       65‑144
                       A. Sovereignty over the disputed territory and alleged breaches
                          thereof 	                                                          65‑99
                       B. Alleged violations of international environmental law	           100‑120

                          1. Procedural obligations	                                       101‑112
                             (a) The alleged breach of the obligation to carry out an
                                 environmental impact assessment	                          101‑105
                             (b) The alleged breach of an obligation to notify and
                                 consult	                                                  106‑111
                             (c) Conclusion	                                                   112
                          2. Substantive   obligations    concerning    transboundary
                             harm	                                                         113‑120
                       C. Compliance with provisional measures	                            121‑129
                       D. Rights of navigation	                                            130‑136
                       E. Reparation	                                                      137‑144
                    IV. Issues in the Nicaragua v. Costa Rica Case 	                       145‑228
                       A. The alleged breach of procedural obligations	                    146‑173
                          1. The alleged breach of the obligation to carry out an
                             environmental impact assessment	                             146‑162
                          2. The alleged breach of Article 14 of the Convention on Bio-
                             logical Diversity	                                            163‑164
                          3. The alleged breach of an obligation to notify and
                             consult	                                                      165‑172
                       B. Alleged breaches of substantive obligations	                     174‑223
                          1. The alleged breach of the obligation not to cause signifi-
                             cant transboundary harm to Nicaragua	                         177‑217
                             (a) The contribution of sediment from the road to the
                                 river181‑186
                             (b) Whether the road‑derived sediment caused significant
                                 harm to Nicaragua	                                  187‑216

                                                                                4

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                       certain activities and construction of a road (judgment) 666

                                (i) Alleged harm caused by increased sediment
                                    concentrations in the river	                       188‑196
                               (ii) Alleged harm to the river’s morphology, to
                                     navigation and to Nicaragua’s dredging pro-

                                     gramme	                                            197‑207
                              (iii) Alleged harm to water quality and the aquatic
                                    ecosystem	                                          208‑213
                              (iv) Other alleged harm	                                  214-216
                          (c) Conclusion	                                                  217
                        2. Alleged breaches of treaty obligations	                      218‑220

                        3. The obligation to respect Nicaragua’s territorial integrity
                           and sovereignty over the San Juan River	                     221‑223
                      C. Reparation	                                                    224‑228
                    Operative Clause	                                                      229

                                                                                5

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                                                                                667

                                   INTERNATIONAL COURT OF JUSTICE

                                                      YEAR 2015                                             2015
                                                                                16 December
                                                   16 December 2015                                     General List
                                                                                Nos. 150 and 152

        CERTAIN ACTIVITIES CARRIED OUT BY NICARAGUA
                    IN THE BORDER AREA
                                         (COSTA RICA v. NICARAGUA)

                                                          AND

                    CONSTRUCTION OF A ROAD IN COSTA RICA
                         ALONG THE SAN JUAN RIVER
                                         (NICARAGUA v. COSTA RICA)

                      Jurisdiction of the Court.

                                                           * *
                       Geographical and historical context and origin of the disputes.
                       The San Juan River, Lower San Juan and Colorado River — Isla Calero and
                    Isla Portillos — Harbor Head Lagoon — Wetlands of international importance —
                    1858 Treaty of Limits — Cleveland Award — Alexander Awards — Dredging of
                    the San Juan by Nicaragua — Activities of Nicaragua in the northern part of
                    Isla Portillos : dredging of a channel (caño) and establishment of a military pres‑
                    ence — Construction of Route 1856 Juan Rafael Mora Porras (the road) by
                    Costa Rica.

                                                           * *
                       Issues in the Costa Rica v. Nicaragua case.
                       Sovereignty over the disputed territory — Definition of “disputed territory” —
                    Description of boundary in 1858 Treaty, Cleveland and Alexander Awards —
                    Articles II and VI of 1858 Treaty to be read together — Sovereignty over right
                    bank of San Juan River as far as its mouth attributed to Costa Rica — Reference
                    to “first channel met” in first Alexander Award — Satellite and aerial images

                                                                                6

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                       certain activities and construction of a road (judgment)                668

                 insufficient to prove caño existed prior to dredging in 2010 — Affidavits of Nica‑
                 raguan State officials also insufficient — Significance of map evidence and effec-
                 tivités limited — Effectivités cannot affect title to sovereignty resulting from
                 1858 Treaty and Cleveland and Alexander Awards — Existence of caño prior to
                 2010 contradicted by other evidence — Nicaragua’s claim would prevent
                 Costa Rica from enjoying territorial sovereignty over the right bank of the San
                 Juan as far as its mouth — Right bank of the caño not part of the boundary —
                 Sovereignty over disputed territory belongs to Costa Rica.

                    Alleged breaches of Costa Rica’s sovereignty — Uncontested that Nicaragua
                 excavated three caños and established a military presence in disputed territory —
                 Costa Rica’s territorial sovereignty breached — Obligation to make reparation —
                 No violation of Article IX of 1858 Treaty — No need to consider possible violation
                 of prohibition of threat or use of force — No need to consider whether conduct of
                 Nicaragua constitutes a military occupation.

                                                         *
                    Alleged violations of international environmental law.
                    Procedural obligations — Obligation to conduct environmental impact assess‑
                 ment concerning activities that risk causing significant transboundary harm —
                 Content of environmental impact assessment depends on specific circumstances —
                 If assessment confirms risk of significant transboundary harm, State planning the
                 activity is required, in conformity with due diligence obligation, to notify and
                 consult with potentially affected State, where necessary to determine appropriate
                 measures to prevent or mitigate risk — Nicaragua’s dredging programme did not
                 give rise to risk of significant transboundary harm — Nicaragua not required to
                 carry out transboundary environmental impact assessment — No obligation under
                 general international law to notify and consult since no risk of significant trans‑
                 boundary harm — No conventional obligation to notify and consult in present
                 case — Court concludes that no procedural obligations breached by Nicaragua.

                    Substantive obligations — Specific obligations concerning San Juan River in
                 1858 Treaty as interpreted by Cleveland Award — Customary law obligation to
                 exercise due diligence to avoid causing significant transboundary harm — No need
                 to discuss relationship between these obligations because no harm established —
                 No proof that dredging of Lower San Juan harmed Costa Rican wetland — Not
                 shown that dredging programme caused significant reduction in flow of Colorado
                 River — Any diversion of water due to dredging did not seriously impair naviga‑
                 tion on Colorado River or otherwise cause harm to Costa Rica — Court concludes
                 that no substantive obligations breached by Nicaragua.

                                                         *

                                                                                7

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                       certain activities and construction of a road (judgment)              669

                   Compliance with provisional measures — Nicaragua breached its obligations
                 under Order of 8 March 2011 by excavating two caños and establishing a military
                 presence in disputed territory in 2013 — Breach of obligations under Court’s
                 Order of 22 November 2013 not established.

                                                        *
                    Rights of navigation — Claim is admissible — Article VI of the 1858 Treaty —
                 Court’s Judgment in Dispute regarding Navigational and Related Rights — No
                 need for the Court to interpret Nicaraguan Decree No. 079‑2009 — Five instances
                 of violations of navigational rights raised by Costa Rica — Two of the five
                 instances examined — Court concludes Nicaragua breached Costa Rica’s naviga‑
                 tional rights pursuant to the 1858 Treaty — Not necessary for Court to consider
                 the other incidents invoked by Costa Rica.

                                                        *
                    Reparation — Requests to order repeal of Decree No. 079‑2009 and cessation
                 of dredging activities cannot be granted — Declaration of breach provides ade‑
                 quate satisfaction for non‑material injury suffered — No need for guarantees of
                 non-repetition — Costa Rica entitled to compensation for material damage —
                 Parties should engage in negotiation on amount of compensation — Failing agree‑
                 ment within 12 months, Court will determine amount at request of one of the Par‑
                 ties — Award of costs under Article 64 of the Statute not appropriate.

                                                       * *
                    Issues in the Nicaragua v. Costa Rica case.
                    Procedural obligations.
                    Alleged breach of obligation to carry out environmental impact assessment —
                 Due diligence obligation requires State to ascertain whether a proposed activity
                 entails risk of significant transboundary harm — Environmental impact assess‑
                 ment required when risk is present — No evidence that Costa Rica determined
                 whether environmental impact assessment was necessary prior to constructing the
                 road — Large scale of road project — Proximity to San Juan River on Nicara‑
                 guan territory — Risk of erosion due to deforestation — Possibility of natural
                 disasters in area — Presence of two wetlands of international importance in
                 area — Construction of road carried a risk of significant transboundary harm —
                 No emergency justifying immediate construction of road — Court need not decide
                 whether there is, in international law, an emergency exemption from obligation to
                 carry out environmental impact assessment — Costa Rica under obligation to con‑
                 duct environmental impact assessment — Obligation requires ex ante evaluation of
                 risk of significant transboundary harm — Environmental Diagnostic Assessment
                 and other studies by Costa Rica were post hoc assessments — Costa Rica has not
                 complied with obligation to carry out environmental impact assessment.

                                                                                8

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                       certain activities and construction of a road (judgment)                  670

                    Alleged breach of Article 14 of Convention on Biological Diversity — No viola‑
                 tion established.
                    Alleged breach of obligation to notify and consult — General international law
                 duty to notify and consult does not call for examination because Costa Rica has
                 not carried out environmental impact assessment — 1858 Treaty did not impose
                 obligation on Costa Rica to notify Nicaragua of construction of road — No proce‑
                 dural obligations arose under Ramsar Convention.

                                                          *
                    Substantive obligations.
                    Alleged breach of obligation to exercise due diligence to prevent causing signifi‑
                 cant transboundary harm — Modelling and estimates by experts suggest sediment
                 due to construction of road amounts to at most 2 per cent of San Juan River’s total
                 load — Actual measurements provided to Court do not indicate that road signifi‑
                 cantly impacted sediment levels in river — Increase in sediment levels as a result of
                 construction of road did not in and of itself cause significant transboundary
                 harm — No significant harm to river’s morphology, to navigation or to Nicara‑
                 gua’s dredging programme established — No proof of significant harm to river’s
                 ecosystem or water quality — Arguments concerning other alleged harm fail.

                     Alleged breaches of treaty obligations — No violation established.

                    Claim concerning violation of territorial integrity and sovereignty — No viola‑
                 tion established.

                                                          *
                     Reparation — Declaration of wrongful conduct in respect of obligation to
                 conduct environmental impact assessment is the appropriate measure of satis
                  faction — No grounds to order Costa Rica to cease continuing wrongful acts —
                 Restitution and compensation not appropriate remedies in absence of significant
                 harm — No need to appoint expert or committee to evaluate harm — Nicaragua’s
                 request to order Costa Rica not to undertake future development without an envi‑
                 ronmental impact assessment dismissed.

                                                   JUDGMENT

                 Present: President Abraham ; Vice‑President Yusuf ; Judges Owada, Tomka,
                           Bennouna, Cançado Trindade, Greenwood, Xue, Donoghue,
                           Gaja, Sebutinde, Bhandari, Robinson, Gevorgian ; Judges ad hoc
                           Guillaume, Dugard ; Registrar Couvreur.

                                                                                9

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                       certain activities and construction of a road (judgment)               671

                    In the case concerning Certain Activities Carried Out by Nicaragua in the Bor‑
                 der Area, and in the joined case (see paragraph 19 below) concerning Construc‑
                 tion of a Road in Costa Rica along the San Juan River,
                     between
                 the Republic of Costa Rica,
                 represented by
                   H.E. Mr. Manuel A. González Sanz, Minister for Foreign Affairs and Wor-
                      ship of Costa Rica ;
                   H.E. Mr. Edgar Ugalde Alvarez, Ambassador on Special Mission,
                   as Agent ;
                   H.E. Mr. Sergio Ugalde, Ambassador of Costa Rica to the Kingdom of the
                      Netherlands, member of the Permanent Court of Arbitration,
                   as Co‑Agent, Counsel and Advocate ;
                   Mr. Marcelo Kohen, Professor of International Law at the Graduate Insti-
                      tute of International and Development Studies, Geneva, member of the
                      Institut de droit international,
                   Mr. Samuel Wordsworth, Q.C., member of the English Bar, member of the
                      Paris Bar, Essex Court Chambers,
                   Mr. Arnoldo Brenes, Senior Adviser to the Ministry of Foreign Affairs and
                      Worship of Costa Rica, member of the Costa Rican Bar,
                   Ms Kate Parlett, Solicitor admitted in Queensland, Australia, and in England
                      and Wales,
                   Ms Katherine Del Mar, member of the English Bar, 4 New Square, Lincoln’s
                      Inn,
                   as Counsel and Advocates ;
                   Mr. Simon Olleson, member of the English Bar, 13 Old Square Chambers,
                   as Counsel ;
                   Mr. Ricardo Otárola, Adviser to the Ministry of Foreign Affairs and Wor-
                      ship of Costa Rica,
                   Ms Shara Duncan, Adviser to the Ministry of Foreign Affairs and Worship
                      of Costa Rica,
                   Mr. Gustavo Campos, Minister Counsellor and Consul General of Costa Rica
                      to the Kingdom of the Netherlands,
                   Mr. Rafael Sáenz, Minister Counsellor at the Costa Rican Embassy in the
                      Kingdom of the Netherlands,
                   Ms Ana Patricia Villalobos, Official at the Ministry of Foreign Affairs and
                      Worship of Costa Rica,
                   as Assistant Counsel ;
                   Ms Elisa Rivero, Administrative Assistant at the Ministry of Foreign Affairs
                      and Worship of Costa Rica,
                   as Assistant,
                     and
                 the Republic of Nicaragua,
                 represented by

                                                                                10

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                       certain activities and construction of a road (judgment)                672

                     H.E. Mr. Carlos José Argüello Gómez, Ambassador of Nicaragua to the
                        Kingdom of the Netherlands,
                     as Agent and Counsel ;
                     Mr. Stephen C. McCaffrey, Professor of International Law at the University
                        of the Pacific, McGeorge School of Law, Sacramento, former member and
                        former Chair of the International Law Commission,
                     Mr. Alain Pellet, Professor at the University Paris Ouest, Nanterre‑La Défense,
                        former member and former Chair of the International Law Commission,
                        member of the Institut de droit international,
                     Mr. Paul S. Reichler, Attorney‑at‑Law, Foley Hoag LLP, member of the
                        Bars of the United States Supreme Court and the District of Columbia,
                     Mr. Andrew B. Loewenstein, Attorney‑at‑Law, Foley Hoag LLP, member of
                        the Bar of the Commonwealth of Massachusetts,
                     as Counsel and Advocates ;
                     Mr. César Vega Masís, Deputy Minister for Foreign Affairs, Director of
                        Juridical Affairs, Sovereignty and Territory, Ministry of Foreign Affairs of
                        Nicaragua,
                     Mr. Walner Molina Pérez, Juridical Adviser, Ministry of Foreign Affairs of
                        Nicaragua,
                     Mr. Julio César Saborio, Juridical Adviser, Ministry of Foreign Affairs of
                        Nicaragua,
                     as Counsel ;
                     Mr. Edgardo Sobenes Obregon, Counsellor, Embassy of Nicaragua in the
                        Kingdom of the Netherlands,
                     Ms Claudia Loza Obregon, First Secretary, Embassy of Nicaragua in the
                        Kingdom of the Netherlands,
                     Mr. Benjamin Samson, Researcher, Centre de droit international de Nanterre
                        (CEDIN), University of Paris Ouest, Nanterre‑La Défense,
                     Ms Cicely O. Parseghian, Attorney‑at‑Law, Foley Hoag LLP, member of the
                        Bar of the Commonwealth of Massachusetts,
                     Mr. Benjamin K. Guthrie, Attorney‑at‑Law, Foley Hoag LLP, member of
                        the Bar of the Commonwealth of Massachusetts,
                     Mr. Ofilio J. Mayorga, Attorney‑at‑Law, Foley Hoag LLP, member of the
                        Bars of the Republic of Nicaragua and New York,
                     as Assistant Counsel ;
                     Mr. Danny K. Hagans, Principal Earth Scientist at Pacific Watershed Associ-
                        ates, Inc.,
                     Mr. Robin Cleverly, Geographical and Technical Consultant,
                     Ms Blanca P. Ríos Touma, Ph.D., Assistant Professor at Universidad Tec-
                        nológica Indoamérica in Quito, Ecuador,
                     Mr. Scott P. Walls, Master of Landscape Architecture — Environmental
                        Planning, Sole Proprietor and Fluvial Geomorphologist at Scott Walls
                        Consulting, Ecohydrologist at cbec ecoengineering, Inc., and Chief Finan-
                        cial Officer and Project Manager at International Watershed Partners,

                     Ms Victoria Leader, Geographical and Technical Consultant,
                     as Scientific Advisers and Experts,

                                                                                11

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                       certain activities and construction of a road (judgment)                673

                     The Court,
                     composed as above,
                     after deliberation,
                     delivers the following Judgment :
                     1. By an Application filed in the Registry of the Court on 18 November 2010,
                 the Republic of Costa Rica (hereinafter “Costa Rica”) instituted proceedings
                 against the Republic of Nicaragua (hereinafter “Nicaragua”) in the case con-
                 cerning Certain Activities Carried Out by Nicaragua in the Border Area
                 (Costa Rica v. Nicaragua) (hereinafter referred to as the “Costa Rica v. Nicara‑
                 gua case”). In that Application, Costa Rica alleges in particular that Nicaragua
                 invaded and occupied Costa Rican territory, and that it dug a channel thereon ;
                 it further reproaches Nicaragua with conducting works (notably dredging of the
                 San Juan River) in violation of its international obligations.
                     2. In its Application, Costa Rica invokes as a basis of the jurisdiction of the
                 Court Article XXXI of the American Treaty on Pacific Settlement adopted at
                 Bogotá on 30 April 1948 (hereinafter the “Pact of Bogotá”). In addition,
                 Costa Rica seeks to found the jurisdiction of the Court on the declaration it
                 made on 20 February 1973 under Article 36, paragraph 2, of the Statute,
                 as well as on the declaration which Nicaragua made on 24 September 1929 (and
                 amended on 23 October 2001) under Article 36 of the Statute of the Permanent
                 Court of International Justice and which is deemed, pursuant to Article 36,
                 paragraph 5, of the Statute of the present Court, for the period which it still has
                 to run, to be acceptance of the compulsory jurisdiction of this Court.
                     3. On 18 November 2010, having filed its Application, Costa Rica also sub-
                 mitted a request for the indication of provisional measures, pursuant to Arti-
                 cle 41 of the Statute and Articles 73, 74 and 75 of the Rules of Court.
                     4. In accordance with Article 40, paragraph 2, of the Statute, the Registrar
                 communicated a signed copy of the Application forthwith to the Government of
                 Nicaragua ; and, under paragraph 3 of that Article, all States entitled to appear
                 before the Court were notified of the filing of the Application.
                     5. Pursuant to the instructions of the Court under Article 43 of the Rules of
                 Court, the Registrar addressed to States parties to the Convention on Wetlands
                 of International Importance especially as Waterfowl Habitat, signed at Ramsar
                 on 2 February 1971 (hereinafter the “Ramsar Convention”), the notification
                 provided for in Article 63, paragraph 1, of the Statute.
                     6. Since the Court included no judge of the nationality of the Parties upon
                 the Bench, each of them, in exercise of the right conferred by Article 31, para-
                 graph 3, of the Statute, chose a judge ad hoc in the case. Costa Rica chose
                 Mr. John Dugard and Nicaragua chose Mr. Gilbert Guillaume.
                     7. By an Order of 8 March 2011 (hereinafter the “Order of 8 March 2011”),
                 the Court, having heard the Parties, indicated provisional measures addressed to
                 both Parties. The Court also directed each Party to inform it about compliance
                 with the provisional measures. By various communications, the Parties each
                 notified the Court of the measures they had taken with reference to the afore-
                 mentioned Order and made observations on the compliance by the other Party
                 with the said Order.

                   8. By an Order of 5 April 2011, the Court fixed 5 December 2011 and
                 6 August 2012 as the respective time‑limits for the filing in the case of a Memo-

                                                                                12

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                       certain activities and construction of a road (judgment)                 674

                 rial by Costa Rica and a Counter‑Memorial by Nicaragua. The Memorial and
                 the Counter‑Memorial were filed within the time‑limits thus prescribed.

                    9. By an Application filed in the Registry on 22 December 2011, Nicaragua
                 instituted proceedings against Costa Rica in the case concerning Construction of
                 a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica) (here-
                 inafter referred to as the “Nicaragua v. Costa Rica case”). In that Application,
                 Nicaragua stated that the case related to “violations of Nicaraguan sovereignty
                 and major environmental damages on its territory”, contending, in particular,
                 that Costa Rica was carrying out major road construction works in the border
                 area between the two countries along the San Juan River, in violation of several
                 international obligations and with grave environmental consequences.

                      10. In its Application, Nicaragua invokes Article XXXI of the Pact of Bogotá
                 as a basis for the jurisdiction of the Court. In addition, Nicaragua seeks to
                 found the jurisdiction of the Court on the aforementioned declarations accept-
                 ing the jurisdiction of the Court (see paragraph 2 above).
                      11. In accordance with Article 40, paragraph 2, of the Statute, the Registrar
                   communicated a signed copy of the Application forthwith to the Government of
                   Costa Rica ; and, under paragraph 3 of that Article, all States entitled to appear
                 before the Court were notified of the filing of the Application.
                      12. Pursuant to the instructions of the Court under Article 43 of its Rules,
                 the Registrar addressed the notifications provided for in Article 63, paragraph 1,
                 of the Statute, to States parties to the Ramsar Convention, to the 1992 Conven-
                 tion on Biological Diversity and to the 1992 Convention for the Conservation
                 of the Biodiversity and Protection of Priority Wilderness Areas in Central
                 America.
                      13. Since the Court included no judge of the nationality of the Parties upon
                 the Bench, each of them, in exercise of the right conferred by Article 31, para-
                  graph 3, of the Statute, chose a judge ad hoc in the case. Nicaragua chose
                   Mr. Gilbert Guillaume and Costa Rica chose Mr. Bruno Simma.
                      14. By an Order of 23 January 2012, the Court fixed 19 December 2012 and
                  19 December 2013 as the respective time‑limits for the filing of a Memorial by
                  Nicaragua and a Counter‑Memorial by Costa Rica. The Memorial and the
                  Counter‑Memorial were filed within the time‑limits thus prescribed.
                      15. In the Counter‑Memorial it filed in the Costa Rica v. Nicaragua case on
                  6 August 2012, Nicaragua submitted four counter‑claims. In its first counter‑
                  claim, it requested the Court to declare that “Costa Rica bears responsibility to
                  Nicaragua” for “the impairment and possible destruction of navigation on the
                  San Juan River caused by the construction of [the] road”. In its second
                  counter‑claim, it asked the Court to declare that it “has become the sole

                  sovereign over the area formerly occupied by the Bay of San Juan del Norte”.
                   In its third counter‑claim, it requested the Court to find that “Nicaragua
                   has a right to free navigation on the Colorado . . . until the conditions of navig
                   ability existing at the time the 1858 Treaty [of Limits] was concluded are
                   re‑established”. Finally, in its fourth counter‑claim, Nicaragua alleged that
                   Costa Rica violated the provisional measures indicated by the Court in its
                   Order of 8 March 2011.

                    16. At a meeting held by the President with the representatives of the Parties
                 on 19 September 2012, the Parties agreed not to request the Court’s authoriza-
                 tion to file a Reply and a Rejoinder in the Costa Rica v. Nicaragua case. At the

                                                                                13

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                       certain activities and construction of a road (judgment)                675

                 same meeting, the Co‑Agent of Costa Rica raised certain objections to the
                 admissibility of the first three counter‑claims contained in the Counter‑Memorial
                 of Nicaragua. He confirmed these objections in a letter of the same day.

                    By letters dated 28 September 2012, the Registrar informed the Parties that
                 the Court had fixed 30 November 2012 and 30 January 2013 as the respective
                 time‑limits for the filing of written observations by Costa Rica and Nicaragua
                 on the admissibility of the latter’s first three counter‑claims. Both Parties filed
                 their observations within the time‑limits thus prescribed.

                   17. By letters dated 19 December 2012, which accompanied its Memorial in
                 the Nicaragua v. Costa Rica case, Nicaragua requested the Court to “decide
                 proprio motu whether the circumstances of the case require[d] the indication of
                 provisional measures” and to consider whether there was a need to join the
                 proceedings in the Nicaragua v. Costa Rica and Costa Rica v. Nicaragua cases.

                    By a letter dated 15 January 2013, the Registrar, acting on the instructions of
                 the President, asked Costa Rica to inform the Court, by 18 February 2013 at the
                 latest, of its views on both questions. Costa Rica communicated its views within
                 the time‑limit thus prescribed.
                    18. By letters dated 11 March 2013, the Registrar informed the Parties that
                 the Court was of the view that the circumstances of the Nicaragua v. Costa Rica
                 case, as they presented themselves to it at that time, were not such as to require
                 the exercise of its power under Article 75 of the Rules of Court to indicate pro-
                 visional measures proprio motu.
                    19. By two separate Orders dated 17 April 2013, the Court joined the pro-
                 ceedings in the Costa Rica v. Nicaragua and Nicaragua v. Costa Rica cases.
                    20. By a communication of the same date, Mr. Simma, who had been chosen
                 by Costa Rica to sit as judge ad hoc in the Nicaragua v. Costa Rica case,
                 informed the Court of his decision to resign from his functions, following
                 the above‑mentioned joinder of proceedings. Thereafter, Judges Guillaume
                 and Dugard sat as judges ad hoc in the joined cases (see paragraphs 6 and 13
                 above).
                    21. By an Order of 18 April 2013, the Court ruled on the admissibility of
                 Nicaragua’s counter‑claims in the Costa Rica v. Nicaragua case. It concluded
                 that there was no need for it to adjudicate on the admissibility of Nicaragua’s
                 first counter‑claim as such. It found the second and third counter‑claims inad-
                 missible as such. The Court also found that there was no need for it to entertain
                 the fourth counter‑claim as such, and that the Parties might take up any ques-
                 tion relating to the implementation of the provisional measures indicated by the
                 Court in its Order of 8 March 2011 in the further course of the proceedings.

                    22. On 23 May 2013, Costa Rica, with reference to Article 41 of the Statute
                 and Article 76 of the Rules of Court, filed with the Registry a request for the
                 modification of the Order indicating provisional measures made on 8 March
                 2011. In its written observations thereon, dated 14 June 2013, Nicaragua asked
                 the Court to reject Costa Rica’s request, while in its turn requesting the Court
                 to otherwise modify the Order of 8 March 2011 on the basis of Article 76 of the
                 Rules of Court. Costa Rica communicated to the Court its written observations
                 on Nicaragua’s request on 20 June 2013.

                                                                                14

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                       23. By an Order of 16 July 2013, the Court found that “the circumstances, as
                 they now present themselves to the Court, are not such as to require the exercise
                 of its power to modify the measures indicated in the Order of 8 March 2011”.
                 The Court however reaffirmed the said provisional measures.
                       24. On 24 September 2013, Costa Rica, with reference to Article 41 of the
                 Statute and Articles 73, 74 and 75 of the Rules of Court, filed with the Registry
                 a request for the indication of new provisional measures in the Costa Rica v.
                   Nicaragua case.
                       25. On 11 October 2013, Nicaragua filed with the Registry a request for the
                   indication of provisional measures in the Nicaragua v. Costa Rica case. Nicara-
                 gua suggested that its request be heard concurrently with Costa Rica’s request
                 for the indication of new provisional measures in the Costa Rica v. Nicaragua
                 case, at a single set of oral proceedings. By letter of 14 October 2013, Costa Rica
                 objected to Nicaragua’s suggestion. By letters dated 14 October 2013, the
                 Registrar informed the Parties that the Court had decided that it would consider
                  the two requests separately.
                       26. By an Order of 22 November 2013 rendered in the Costa Rica v. Nicara‑
                   gua case, the Court, having heard the Parties, reaffirmed the provisional
                  measures indicated in its Order of 8 March 2011 and indicated new provisional
                   measures addressed to both Parties. The Court also directed each Party to inform
                   it, at three‑month intervals, as to compliance with the provisional measures. By
                   various communications, each of the Parties notified the Court of the measures
                   they had taken with reference to the aforementioned Order and made observa-
                   tions on the compliance by the other Party with the said Order.

                    27. By an Order of 13 December 2013 rendered in the Nicaragua v. Costa Rica
                 case, the Court, after hearing the Parties, found “that the circumstances, as they
                 now present themselves to the Court, are not such as to require the exercise of
                 its power under Article 41 of the Statute to indicate provisional measures”.

                     28. At a meeting held by the President with the representatives of the Parties
                 on 22 January 2014, Nicaragua requested the Court to authorize a second round
                 of written pleadings in the Nicaragua v. Costa Rica case, while Costa Rica
                 objected. By an Order of 3 February 2014, the Court authorized the submission
                 of a Reply by Nicaragua and a Rejoinder by Costa Rica, and fixed 4 August
                 2014 and 2 February 2015 as the respective time‑limits for the filing of those
                 pleadings. The Reply of Nicaragua and the Rejoinder of Costa Rica were duly
                 filed within the time‑limits so prescribed.

                    29. By letters dated 2 April 2014, the Registrar informed the Parties that the
                 Court, in accordance with Article 54, paragraph 1, of the Rules of Court, had
                 fixed 3 March 2015 as the date for the opening of the oral proceedings in the
                 joined cases.
                    30. In a letter dated 4 August 2014, which accompanied its Reply in the Nica‑
                 ragua v. Costa Rica case, Nicaragua suggested that the Court appoint “a neutral
                 expert on the basis of Articles 66 and 67 of the Rules”. By letter of 14 August
                 2014, Costa Rica indicated that it was of the view “that there [was] no basis for
                 the Court to exercise its power to appoint an expert as requested by Nicaragua”.
                    31. By a letter dated 15 October 2014, Nicaragua requested that the opening
                 of the oral proceedings in the joined cases be postponed until May 2015. On the
                 basis that Costa Rica had stated, in its letter of 14 August 2014 referred to in the
                 previous paragraph, that the evidence submitted by the Parties “w[ould] be sup-

                                                                                15

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                 plemented and completed” in Costa Rica’s Rejoinder in the Nicaragua v.
                 Costa Rica case, Nicaragua expressed the view that it would be “inadequate and
                 inequitable for [it] to have less than one month to analyze and respond to
                 Costa Rica’s new scientific information and expert reports”. By letter of 20 Octo-
                 ber 2014, Costa Rica opposed this request, arguing in particular that any delay
                 in the Court hearing and adjudging the Costa Rica v. Nicaragua case would
                 prejudice Costa Rica, that Nicaragua had sufficient time to analyse the Rejoin-
                 der and formulate its response before the commencement of the hearings,
                 and that Nicaragua’s request was belated. By letters dated 17 November 2014,
                 the Registrar informed the Parties that the Court had decided to postpone
                 the date for the opening of the oral proceedings in the joined cases until 14 April
                 2015.
                    32. By letters dated 5 December 2014, referring to the communications men-
                 tioned in paragraph 30 above, the Registrar informed the Parties that the Court
                 would find it useful if, during the course of the hearings in the two cases, they could
                 call the experts whose reports were annexed to the written pleadings, in particular
                 Mr. Thorne and Mr. Kondolf. The Registrar also indicated that the Court would
                 be grateful if, by 15 January 2015 at the latest, the Parties would make suggestions
                 regarding the modalities of the examination of those experts. Such suggestions
                 were received from Nicaragua within the time‑limit indicated. By a letter dated
                 20 January 2015, Costa Rica commented on the suggestions of Nicaragua.
                    33. In a letter dated 2 February 2015, which accompanied its Rejoinder in the
                 Nicaragua v. Costa Rica case, Costa Rica raised the possibility of a site visit to
                 the “location of the Road”. By a letter dated 10 February 2015, Nicaragua
                 expressed its willingness to assist to the fullest possible extent in the organiza-
                 tion “of such a visit at the location of the road and the San Juan de Nicaragua
                 River”. It also reiterated its proposal that the Court appoint an expert (see para-
                 graph 30 above) to assess the construction of the road, and suggested that the
                 expert be included in the Court’s delegation for any site visit. By a letter dated
                 11 February 2015, Costa Rica commented on Nicaragua’s letter of 10 February
                 2015, stating in particular that the appointment of an expert by the Court was
                 unnecessary. By letters dated 25 February 2015, the Registrar informed the Par-
                 ties that the Court had decided not to carry out a site visit.

                    34. By letters of the Registrar dated 4 February 2015, the Parties were
                 informed that they should indicate to the Court, by 2 March 2015 at the latest,
                 the names of the experts they intended to call, and communicate the other infor-
                 mation required by Article 57 of the Rules of Court. The Parties were also
                 instructed to provide the Court, by 16 March 2015 at the latest, with written
                 statements of these experts (limited to a summary of the expert’s own reports or
                 to observations on other expert reports in the case file), and were informed that
                 these would replace the examination‑in‑chief. In addition, the Court invited the
                 Parties to come to an agreement as to the allocation of time for the cross‑exam-
                 ination and re‑examination of experts by 16 March 2015 at the latest.
                    By the same letters, the Registrar also notified the Parties of the following
                 details regarding the procedure for examining the experts. After having made
                 the solemn declaration required under Article 64 of the Rules of Court, the
                 expert would be asked by the Party calling him to endorse his written statement.
                 The other Party would then have an opportunity for cross‑examination on the
                 contents of the expert’s written statement or his earlier reports. Re‑examination
                 would thereafter be limited to subjects raised in cross‑examination. Finally, the
                 judges would have an opportunity to put questions to the expert.

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                    35. By letters dated 2 March 2015, the Parties indicated the names of the
                 experts they wished to call at the hearings, and provided the other information
                 concerning them required by Article 57 of the Rules of Court (see paragraph 34
                 above).
                    36. Under cover of a letter dated 3 March 2015, Costa Rica communicated
                 to the Court a video which it wished to be included in the case file and presented
                 at the hearings. By a letter dated 13 March 2015, Nicaragua stated that it had
                 no objection to Costa Rica’s request and presented certain comments on the
                 utility of the video ; it also announced that it would produce photographs in
                 response. By letters dated 23 March 2015, the Registrar informed the Parties
                 that the Court had decided to grant Costa Rica’s request.

                    37. By letters dated 16 March 2015, the Parties communicated the written
                 statements of the experts they intended to call at the hearings. Costa Rica also
                 asked the Court to extend to 20 March 2015 the time‑limit within which the Par-
                 ties might transmit an agreement or their respective positions regarding the allo-
                 cation of time for the cross‑examination and re‑examination of those experts,
                 which was granted by the Court. However, since the Parties were unable to
                 agree fully on this matter within the time‑limit thus extended, the Registrar
                 informed them, by letters of 23 March 2015, of the Court’s decision in respect of
                 the maximum time that could be allocated for the examinations. In this connec-
                 tion, the Parties were invited to indicate the order in which they wished to pres-
                 ent their experts, and the precise amount of time they wished to reserve for the
                 cross‑examination of each of the experts called by the other Party, which they
                 did by letters dated 30 March and 2 April 2015. By letters dated 10 April 2015,
                 the Registrar communicated to the Parties the detailed schedule for the exam
                 ination of the experts, as adopted by the Court.
                    38. By letters of 23 March 2015, the Registrar informed the Parties that, in
                 relation to the Nicaragua v. Costa Rica case, the Court wished each of them to
                 produce, by 10 April 2015 at the latest, a map showing the San Juan River and
                 the road constructed by Costa Rica, and indicating the precise locations dis-
                 cussed in the key studies referred to in the written statements provided to the
                 Court on 16 March 2015 (see paragraph 37 above). Under cover of letters dated
                 10 April 2015, Nicaragua and Costa Rica each provided the Court with printed
                 and electronic versions of the maps they had prepared.

                    39. By a letter dated 23 March 2015, Nicaragua, as announced (see para-
                 graph 36 above), communicated to the Court photographs that it wished to be
                 included in the case file. By a letter dated 31 March 2015, Costa Rica informed
                 the Court that it had no objection to Nicaragua’s request. By letters dated
                 8 April 2015, the Registrar informed the Parties that the Court had decided to
                 grant Nicaragua’s request.
                    40. By a letter dated 13 April 2015, Costa Rica requested that Nicaragua file
                 a copy of the report of Ramsar Advisory Mission No. 72 in relation to Nicara-
                 gua’s Refugio de Vida Silvestre Río San Juan (San Juan River Wildlife Refuge).
                 By a letter dated 16 April 2015, Nicaragua indicated that it was in possession
                 only of a draft report, in Spanish, which it enclosed with its letter. Subsequently,
                 under cover of a letter dated 24 April 2015, Nicaragua transmitted to the Court
                 the comments it had submitted on 30 November 2011 on the draft report of the
                 Ramsar Advisory Mission (original Spanish version and English translation of
                 certain extracts), as well as the reply from the Ramsar Secretariat dated
                 19 December 2011 (original Spanish version only). The Parties later provided

                                                                                17

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                 the Court with English translations of the documents submitted in Spanish by
                 Nicaragua.

                    41. By a letter dated 21 April 2015, the Registrar informed the Parties that
                 the Court had decided to request, under Article 62 of its Rules, that Nicaragua
                 produce the full text of two documents, excerpts of which were annexed to its
                 Counter‑Memorial in the Costa Rica v. Nicaragua case. By a letter dated
                 24 April 2015, Nicaragua communicated to the Court the full text of the original
                 Spanish versions of the documents requested. Certified English translations were
                 transmitted by Nicaragua under cover of a letter dated 15 May 2015.

                    42. By letter of 28 April 2015, Costa Rica asked for photographs to be
                 included in the Nicaragua v. Costa Rica case file. In a letter dated 29 April 2015,
                 Nicaragua stated that it objected to this request, which it considered had been
                 made too late. By letters dated 29 April 2015, the Registrar informed the Parties
                 that the Court had decided not to grant Costa Rica’s request.

                                                         *
                    43. In accordance with Article 53, paragraph 2, of the Rules of Court, after
                 ascertaining the views of the Parties, the Court decided that copies of the plead-
                 ings and documents annexed would be made accessible to the public at the
                 opening of the oral proceedings.
                    44. Public hearings were held in the joined cases from 14 April 2015 to 1 May
                 2015. Between 14 and 17 April 2015 and 28 and 29 April 2015, the hearings
                 focused on the Costa Rica v. Nicaragua case, and between 20 and 24 April 2015
                 and 30 April and 1 May 2015 on the Nicaragua v. Costa Rica case. The Court
                 heard the oral arguments and replies of :
                 In the Costa Rica v. Nicaragua case,
                 For Costa Rica: H.E. Mr. Edgar Ugalde Alvarez,
                                  H.E. Mr. Sergio Ugalde,
                                  Mr. Arnoldo Brenes,
                                  Mr. Samuel Wordsworth,
                                  Mr. Marcelo Kohen,
                                  Ms Kate Parlett,
                                  Ms Katherine Del Mar.
                 For Nicaragua: H.E. Mr. Carlos José Argüello Gómez,
                                  Mr. Alain Pellet,
                                  Mr. Paul S. Reichler,
                                  Mr. Andrew B. Loewenstein,
                                  Mr. Stephen C. McCaffrey.
                 In the Nicaragua v. Costa Rica case,
                 For Nicaragua: H.E. Mr. Carlos José Argüello Gómez,
                                 Mr. Paul S. Reichler,
                                 Mr. Andrew B. Loewenstein,
                                 Mr. Stephen C. McCaffrey,
                                 Mr. Alain Pellet.
                 For Costa Rica: H.E. Mr. Edgar Ugalde Alvarez,
                                 Mr. Arnoldo Brenes,

                                                                                18

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                                 Ms Katherine Del Mar,
                                 Mr. Marcelo Kohen,
                                 Mr. Samuel Wordsworth,
                                 Ms Kate Parlett,
                                 H.E. Mr. Sergio Ugalde.

                    45. In the Costa Rica v. Nicaragua case, Costa Rica called Mr. Thorne as an
                 expert during the public hearing of 14 April 2015 (afternoon). Later, during the
                 public hearing of 17 April 2015 (morning), Nicaragua called the following
                 experts : Mr. van Rhee and Mr. Kondolf. In the Nicaragua v. Costa Rica case,
                 Nicaragua called the following experts during the public hearings of
                 20 April 2015 (morning and afternoon) : Mr. Weaver, Mr. Kondolf, Mr. Andrews
                 and Mr. Sheate. Costa Rica called Mr. Cowx and Mr. Thorne as experts during
                 the public hearing of 24 April 2015 (morning). A number of judges put ques-
                 tions to the experts, to which replies were given orally.
                    46. At the hearings, Members of the Court also put questions to the Parties,
                 to which replies were given orally, in accordance with Article 61, paragraph 4,
                 of the Rules of Court.

                                                       * *
                   47. In its Application filed in the Costa Rica v. Nicaragua case, Costa Rica
                 made the following claims :
                         “For these reasons, and reserving the right to supplement, amplify or
                      amend the present Application, Costa Rica requests the Court to adjudge
                      and declare that Nicaragua is in breach of its international obligations as
                      referred to in paragraph 1 of this Application as regards the incursion into
                      and occupation of Costa Rican territory, the serious damage inflicted to its
                      protected rainforests and wetlands, and the damage intended to the Colo-
                      rado River, wetlands and protected ecosystems, as well as the dredging and
                      canalization activities being carried out by Nicaragua on the San Juan
                      River.
                         In particular the Court is requested to adjudge and declare that, by its
                      conduct, Nicaragua has breached :
                      (a) the territory of the Republic of Costa Rica, as agreed and delimited by
                          the 1858 Treaty of Limits, the Cleveland Award and the first and second
                          Alexander Awards ;
                      (b) the fundamental principles of territorial integrity and the prohibition
                          of use of force under the Charter of the United Nations and the
                          Charter of the Organization of American States ;
                      (c) the obligation imposed upon Nicaragua by Article IX of the 1858 Treaty
                          of Limits not to use the San Juan River to carry out hostile acts ;
                      (d) the obligation not to damage Costa Rican territory ;
                      (e) the obligation not to artificially channel the San Juan River away from
                           its natural watercourse without the consent of Costa Rica ;
                      (f) the obligation not to prohibit the navigation on the San Juan River by
                           Costa Rican nationals ;
                      (g) the obligation not to dredge the San Juan River if this causes damage
                           to Costa Rican territory (including the Colorado River), in accordance
                           with the 1888 Cleveland Award ;

                                                                                19

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                      (h) the obligations under the Ramsar Convention on Wetlands ;

                      (i) the obligation not to aggravate and extend the dispute by adopting
                          measures against Costa Rica, including the expansion of the invaded
                          and occupied Costa Rican territory or by adopting any further measure
                          or carrying out any further actions that would infringe Costa Rica’s
                          territorial integrity under international law.”

                    Costa Rica also requested the Court to “determine the reparation which must
                 be made by Nicaragua, in particular in relation to any measures of the kind
                 referred to . . . above”.
                    48. In the course of the written proceedings in the Costa Rica v. Nicaragua
                 case, the following submissions were presented by the Parties :

                 On behalf of the Government of Costa Rica,
                 in the Memorial :
                        “For these reasons, and reserving the right to supplement, amplify or
                      amend the present submissions :
                        1. Costa Rica requests the Court to adjudge and declare that, by its
                      conduct, Nicaragua has breached :
                      (a) the obligation to respect the sovereignty and territorial integrity of the
                          Republic of Costa Rica, within the boundaries delimited by the
                          1858 Treaty of Limits and further defined by the Demarcation Com-
                          mission established by the Pacheco‑Matus Convention, in particular by
                          the first and second Alexander Awards ;
                      (b) the prohibition of use of force under Article 2 (4) of the United Nations
                          Charter and Articles 1, 19, 21 and 29 of the Charter of the Organization
                          of American States ;

                      (c) the obligation of Nicaragua under Article IX of the 1858 Treaty of
                          Limits not to use the San Juan to carry out hostile acts ;

                      (d) the rights of Costa Rican nationals to free navigation on the San Juan
                          in accordance with the 1858 Treaty of Limits, the Cleveland Award and
                          the Court’s Judgment of 13 July 2009 ;
                      (e) the obligation not to dredge, divert or alter the course of the San Juan,
                          or conduct any other works on the San Juan, if this causes damage to
                          Costa Rican territory (including the Colorado River), its environment,
                          or to Costa Rican rights in accordance with the Cleveland Award ;

                      (f) the obligation to consult with Costa Rica about implementing obliga-
                          tions arising from the Ramsar Convention, in particular the obligation
                          to co‑ordinate future policies and regulations concerning the conserva-
                          tion of wetlands and their flora and fauna under Article 5 (1) of the
                          Ramsar Convention ; and

                      (g) the Court’s Order for Provisional Measures of 8 March 2011 ;

                                                                                20

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                     and further to adjudge and declare that Nicaragua is :
                     (h) obliged to cease such breaches and to make reparation therefore.

                        2. The Court is requested to order, in consequence, that Nicaragua :
                     (a) withdraw any presence, including all troops and other personnel
                         (whether civilian, police or security, or volunteers) from that part of
                         Costa Rica known as Isla Portillos, on the right bank of the San Juan,
                         and prevent any return there of any such persons ;

                     (b) cease all dredging activities on the San Juan in the area between the
                         point of bifurcation of the Colorado River and the San Juan and the
                         outlet of the San Juan in the Caribbean Sea (‘the area’), pending :
                           (i) an adequate environmental impact assessment ;

                           (ii) notification to Costa Rica of further dredging plans for the area, not
                                less than three months prior to the implementation of such plans ;
                          (iii) due consideration of any comments of Costa Rica made within one
                                month of notification ;

                     (c) not engage in any dredging operations or other works in the area if and
                         to the extent that these may cause significant harm to Costa Rican
                         territory (including the Colorado River) or its environment, or to
                         impair Costa Rica’s rights under the Cleveland Award.

                       3. The Court is also requested to determine, in a separate phase, the
                     reparation and satisfaction to be made by Nicaragua.”
                 On behalf of the Government of Nicaragua,
                 in the Counter‑Memorial :
                        “For the reasons given herein, the Republic of Nicaragua requests the
                     Court to :
                     (1) dismiss and reject the requests and submissions of Costa Rica in her
                         pleadings ;
                     (2) adjudge and declare that :
                            (i) Nicaragua enjoys full sovereignty over the caño joining Harbor
                                Head Lagoon with the San Juan River proper, the right bank of
                                which constitutes the land boundary as established by the
                                1858 Treaty as interpreted by the Cleveland and Alexander
                                Awards ;
                           (ii) Costa Rica is under an obligation to respect the sovereignty and
                                territorial integrity of Nicaragua, within the boundaries delimited
                                by the 1858 Treaty of Limits as interpreted by the Cleveland and
                                Alexander Awards ;
                          (iii) Nicaragua is entitled, in accordance with the 1858 Treaty as inter-
                                preted by the subsequent arbitral awards, to execute works to
                                improve navigation on the San Juan River as it deems suitable,
                                and that these works include the dredging of the San Juan de Nic-
                                aragua River ; and,

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                          (iv) in so doing, Nicaragua is entitled as it deems suitable to re‑establish
                               the situation that existed at the time the 1858 Treaty was concluded ;
                           (v) the only rights enjoyed by Costa Rica on the San Juan de Nicara-
                               gua River are those defined by said Treaty as interpreted by the
                               Cleveland and Alexander Awards.”
                   49. At the oral proceedings in the joined cases, the following submissions
                 were presented by the Parties in the Costa Rica v. Nicaragua case :
                 On behalf of the Government of Costa Rica,
                 at the hearing of 28 April 2015 :
                        “For the reasons set out in the written and oral pleadings, the Republic
                     of Costa Rica requests the Court to :
                     (1) reject all Nicaraguan claims ;
                     (2) adjudge and declare that :
                     (a) sovereignty over the ‘disputed territory’, as defined by the Court in its
                         Orders of 8 March 2011 and 22 November 2013, belongs to the Repub-
                         lic of Costa Rica ;
                     (b) by occupying and claiming Costa Rican territory, Nicaragua has
                         breached :
                            (i) the obligation to respect the sovereignty and territorial integrity of
                                the Republic of Costa Rica, within the boundaries delimited by the
                                1858 Treaty of Limits and further defined by the Demarcation
                                Commission established by the Pacheco‑Matus Convention, in
                                particular by the first and second Alexander Awards ;
                           (ii) the prohibition of the threat or use of force under Article 2 (4) of
                                the Charter of the United Nations and Article 22 of the Charter
                                of the Organization of American States ;
                          (iii) the prohibition to make the territory of other States the object,
                                even temporarily, of military occupation, contrary to Article 21 of
                                the Charter of the Organization of American States ; and
                          (iv) the obligation of Nicaragua under Article IX of the 1858 Treaty of
                                Limits not to use the San Juan River to carry out hostile acts ;
                     (c) by its further conduct, Nicaragua has breached :
                            (i) the obligation to respect Costa Rica’s territory and environment,
                                including its wetland of international importance under the
                                Ramsar Convention ‘Humedal Caribe Noreste’, on Costa Rican
                                territory ;
                           (ii) Costa Rica’s perpetual rights of free navigation on the San Juan
                                in accordance with the 1858 Treaty of Limits, the 1888 Cleveland
                                Award and the Court’s Judgment of 13 July 2009 ;
                          (iii) the obligation to inform and consult with Costa Rica about
                                any dredging, diversion or alteration of the course of the San Juan
                                River, or any other works on the San Juan River that may
                                cause damage to Costa Rican territory (including the Colorado
                                River), its environment, or Costa Rican rights, in accordance
                                with the 1888 Cleveland Award and relevant treaty and customary
                                law ;
                          (iv) the obligation to carry out an appropriate transboundary environ-

                                                                                22

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                                mental impact assessment, which takes account of all potential
                                significant adverse impacts on Costa Rican territory ;
                           (v) the obligation not to dredge, divert or alter the course of the San
                                Juan River, or conduct any other works on the San Juan River, if
                                this causes damage to Costa Rican territory (including the Colo-
                                rado River), its environment, or to Costa Rican rights under the
                                1888 Cleveland Award ;
                          (vi) the obligations arising from the Orders of the Court indicat-
                                ing provisional measures of 8 March 2011 and 22 November
                                2013 ;
                         (vii) the obligation to consult with Costa Rica on the implementation
                                of obligations arising from the Ramsar Convention, in particular
                                the obligation to co‑ordinate future policies and regulations con-
                                cerning the conservation of wetlands and their flora and fauna
                                under Article 5 (1) of the Ramsar Convention ; and
                         (viii) the agreement between the Parties, established in the exchange of
                                notes dated 19 and 22 September 2014, concerning navigation on
                                the San Juan River by Costa Rica to close the eastern caño con-
                                structed by Nicaragua in 2013 ;
                     (d) Nicaragua may not engage in any dredging operations or other works
                         if and to the extent that these may cause damage to Costa Rican terri-
                         tory (including the Colorado River) or its environment, or which
                         may impair Costa Rica’s rights under the 1888 Cleveland Award,
                         including its right not to have its territory occupied without its express
                         consent ;
                     (3) to order, in consequence, that Nicaragua must :
                     (a) repeal, by means of its own choosing, those provisions of the Decree
                         No. 079‑2009 and the Regulatory Norms annexed thereto of 1 October
                         2009 which are contrary to Costa Rica’s right of free navigation under
                         Article VI of the 1858 Treaty of Limits, the 1888 Cleveland Award, and
                         the Court’s Judgment of 13 July 2009 ;
                     (b) cease all dredging activities on the San Juan River in the vicinity of
                         Delta Costa Rica and in the lower San Juan River, pending :
                           (i) an appropriate transboundary environmental impact assessment,
                               which takes account of all potential significant adverse impacts on
                               Costa Rican territory, carried out by Nicaragua and provided to
                               Costa Rica ;
                          (ii) formal written notification to Costa Rica of further dredging plans
                               in the vicinity of Delta Costa Rica and in the lower San Juan
                               River, not less than three months prior to the implementation of
                               any such plans ; and
                         (iii) due consideration of any comments made by Costa Rica upon
                               receipt of said notification ;
                     (c) make reparation in the form of compensation for the material damage
                         caused to Costa Rica, including but not limited to :
                           (i) damage arising from the construction of artificial caños and
                               destruction of trees and vegetation on the ‘disputed territory’ ;

                                                                                23

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                           (ii) the cost of the remediation measures carried out by Costa Rica in
                                relation to those damages, including but not limited to those taken
                                to close the eastern caño constructed by Nicaragua in 2013, pur-
                                suant to paragraph 59 (2) (E) of the Court’s Order on provisional
                                measures of 22 November 2013 ;

                          		 the amount of such compensation to be determined in a separate
                             phase of these proceedings ;
                      (d) provide satisfaction so to achieve full reparation of the injuries caused
                          to Costa Rica in a manner to be determined by the Court ;

                      (e) provide appropriate assurances and guarantees of non‑repetition of
                          Nicaragua’s unlawful conduct, in such a form as the Court may order ;
                          and
                      (f) pay all of the costs and expenses incurred by Costa Rica in requesting
                          and obtaining the Order on provisional measures of 22 November 2013,
                          including, but not limited to, the fees and expenses of Costa Rica’s
                          counsel and experts, with interest, on a full indemnity basis.”

                 On behalf of the Government of Nicaragua,
                 at the hearing of Wednesday 29 April 2015 :
                    “In accordance with Article 60 of the Rules and the reasons given during the
                 written and oral phase of the pleadings the Republic of Nicaragua respectfully
                 requests the Court to :
                      (a) dismiss and reject the requests and submissions of the Republic of
                          Costa Rica ;
                      (b) adjudge and declare that :
                            (i) Nicaragua enjoys full sovereignty over the caño joining Harbor
                                Head Lagoon with the San Juan River proper, the right bank of
                                which constitutes the land boundary as established by the
                                1858 Treaty as interpreted by the Cleveland and Alexander Awards ;
                           (ii) Costa Rica is under an obligation to respect the sovereignty and
                                territorial integrity of Nicaragua, within the boundaries delimited
                                by the 1858 Treaty of Limits as interpreted by the Cleveland and
                                Alexander Awards ;
                          (iii) Nicaragua is entitled, in accordance with the 1858 Treaty as inter-
                                preted by the subsequent arbitral awards, to execute works to
                                improve navigation on the San Juan River as it deems suitable,
                                and that these works include the dredging of the San Juan de Nic-
                                aragua River ;
                          (iv) the only rights enjoyed by Costa Rica on the San Juan de Nicara-
                                gua River are those defined by said Treaty as interpreted by the
                                Cleveland and Alexander Awards.”

                                                         *
                   50. In its Application filed in the Nicaragua v. Costa Rica case, Nicaragua
                 made the following claims :

                                                                                24

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                       “On the basis of the foregoing statement of facts and law, Nicaragua,
                     while reserving the right to supplement, amend or modify this Application,
                     requests the Court to adjudge and declare that Costa Rica has breached :
                     (a) its obligation not to violate Nicaragua’s territorial integrity as delim-
                         ited by the 1858 Treaty of Limits, the Cleveland Award of 1888 and
                         the five Awards of the Umpire E. P. Alexander of 30 September 1897,
                         20 December 1897, 22 March 1898, 26 July 1899 and 10 March 1900 ;

                     (b) its obligation not to damage Nicaraguan territory ;

                     (c) its obligations under general international law and the relevant environ-
                          mental conventions, including the Ramsar Convention on Wetlands,
                          the Agreement over the Border Protected Areas between Nicaragua
                          and Costa Rica (International System of Protected Areas for
                         Peace [SI‑A‑PAZ] Agreement), the Convention on Biological Diver-
                         sity and the Convention for the Conservation of the Biodiversity and
                         Protection of the Main Wildlife Areas [Priority Wilderness Areas] in
                          Central America.
                       Furthermore, Nicaragua requests the Court to adjudge and declare that
                     Costa Rica must :
                     (a) restore the situation to the status quo ante ;
                     (b) pay for all damages caused including the costs added to the dredging
                         of the San Juan River ;
                     (c) not undertake any future development in the area without an appro-
                         priate transboundary environmental impact assessment and that this
                         assessment must be presented in a timely fashion to Nicaragua for its
                         analysis and reaction.
                       Finally, Nicaragua requests the Court to adjudge and declare that Costa
                     Rica must :
                     (a) cease all the constructions underway that affect or may affect the rights
                         of Nicaragua ;
                     (b) produce and present to Nicaragua an adequate environmental impact
                         assessment with all the details of the works.”
                   51. In the course of the written proceedings in the Nicaragua v. Costa Rica
                 case, the following submissions were presented by the Parties :
                 On behalf of the Government of Nicaragua,
                 in the Memorial :
                       “1. For the reasons given herein, the Republic of Nicaragua requests the
                     Court to adjudge and declare that, by its conduct, Costa Rica has breached :

                       (i) its obligation not to violate the integrity of Nicaragua’s territory as
                           delimited by the 1858 Treaty of Limits, the Cleveland Award of 1888
                           and the five Awards of the Umpire E. P. Alexander of 30 Septem-
                           ber 1897, 20 December 1897, 22 March 1898, 26 July 1899 and
                           10 March 1900 ;
                      (ii) its obligation not to damage Nicaraguan territory ;

                                                                                25

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                     (iii) its obligations under general international law and the relevant environ-
                           mental conventions, including the Ramsar Convention on Wetlands,
                           the Agreement over the Border Protected Areas between Nicaragua
                           and Costa Rica (International System of Protected Areas for
                           Peace [SI‑A‑PAZ] Agreement), the Convention on Biological Diver-
                           sity and the Convention for the Conservation of the Biodiversity and
                           Protection of the Main Wildlife Sites [Priority Wilderness Areas] in
                           Central America.
                       2. Furthermore, Nicaragua requests the Court to adjudge and declare
                     that Costa Rica must :
                       (i) cease all the constructions underway that affects or may affect the rights
                           of Nicaragua ;
                      (ii) restore the situation to the status quo ante ;
                     (iii) compensate for all damages caused including the costs added to the
                           dredging of the San Juan de Nicaragua River, with the amount of the
                           compensation to be determined in a subsequent phase of the case ;

                     (iv) not to continue or undertake any future development in the area with-
                          out an appropriate transboundary environmental impact assessment
                          and that this assessment must be presented in a timely fashion to Nica
                          ragua for its analysis and reaction.

                       3. The Republic of Nicaragua further requests the Court to adjudge and
                     declare that :
                       (i) Nicaragua is entitled, in accordance with the 1858 Treaty as interpreted
                            by the subsequent arbitral awards, to execute works to improve navi-
                            gation on the San Juan River as it deems suitable, and that these works
                            include the dredging of the San Juan de Nicaragua River to remove
                            sedimentation and other barriers to navigation ; and,
                      (ii) in so doing, Nicaragua is entitled to re‑establish the conditions of nav-
                           igation that existed at the time the 1858 Treaty was concluded ;
                     (iii) that the violations of the 1858 Treaty and under many rules of interna-
                           tional law by Costa Rica, allow Nicaragua to take appropriate
                           countermeasures including the suspension of Costa Rica’s right of nav-
                            igation in the San Juan de Nicaragua River.

                        4. Finally, Nicaragua requests the Court to order Costa Rica to imme-
                     diately take the emergency measures recommended by its own experts and
                     further detailed in the Kondolf Report, in order to alleviate or mitigate the
                     continuing damage being caused to the San Juan de Nicaragua River and
                     the surrounding environment.
                        If Costa Rica does not of itself proceed to take these measures and the
                     Court considers it cannot order that it be done without the full procedure
                     contemplated in Articles 73 et seq. of the Rules of Court, the Republic of
                     Nicaragua reserves its right to request provisional measures on the basis of
                     Article 41 of the Statute and the pertinent procedures of Article 73 and ff.
                     of the Rules of Court and to amend and modify these submissions in the
                     light of the further pleadings in this case.”

                                                                                26

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                 in the Reply :
                          “For the reasons given in its Memorial and in this Reply, the Republic
                      of Nicaragua requests the Court to adjudge and declare that, by its conduct,
                      the Republic of Costa Rica has breached :
                        (i) its obligation not to violate the integrity of Nicaragua’s territory as
                            delimited by the 1858 Treaty of Limits as interpreted by the Cleveland
                            Award of 1888 and the five Awards of the Umpire E. P. Alexander of
                            30 September 1897, 20 December 1897, 22 March 1898, 26 July 1899,
                            and 10 March 1900 ;

                      (ii) its obligation not to damage Nicaraguan territory ;

                      (iii) its obligations under general international law and the relevant environ-
                            mental conventions, including the Ramsar Convention on Wetlands,
                            the Agreement over the Border Protected Areas between Nicaragua
                            and Costa Rica (International System of Protected Areas for
                            Peace [SI‑A‑PAZ] Agreement), the Convention on Biological Diver-
                            sity and the Convention for the Conservation of the Biodiversity and
                            Protection of the Main Wildlife Sites [Priority Wilderness Areas] in
                            Central America.
                        2. Nicaragua also requests the Court to adjudge and declare that
                      Costa Rica must :
                       (i) cease all its continuing internationally wrongful acts that affect or are
                           likely to affect the rights of Nicaragua ;

                       (ii) inasmuch as possible, restore the situation to the status quo ante, in full
                            respect of Nicaragua’s sovereignty over the San Juan de Nicaragua
                            River, including by taking the emergency measures necessary to allevi-
                            ate or mitigate the continuing harm being caused to the river and the
                            surrounding environment ;
                      (iii) compensate for all damages caused insofar as they are not made good
                            by restitution, including the costs added to the dredging of the San Juan
                            de Nicaragua River, with the amount of the compensation to be deter-
                            mined in a subsequent phase of the case.
                        3. Furthermore, Nicaragua requests the Court to adjudge and declare
                      that Costa Rica must :
                       (i) not undertake any future development in the area without an appro-
                           priate transboundary environmental impact assessment and that this
                           assessment must be presented in a timely fashion to Nicaragua for its
                           analysis and reaction ;
                      (ii) refrain from using Route 1856 to transport hazardous material as long
                           as it has not given the guarantees that the road complies with the best
                           construction practices and the highest regional and international stand-
                           ards of security for road traffic in similar situations.

                        4. The Republic of Nicaragua further requests the Court to adjudge and
                      declare that Nicaragua is entitled :
                       (i) in accordance with the 1858 Treaty as interpreted by the subsequent
                           arbitral awards, to execute works to improve navigation on the San

                                                                                27

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                           Juan River and that these works include the dredging of the San Juan
                           de Nicaragua River to remove sedimentation and other barriers to nav-
                           igation ; and,
                      (ii) in so doing, to re‑establish the conditions of navigation foreseen in the
                           1858 Treaty.
                         5. Finally, if the Court has not already appointed a neutral expert at the
                      time when it adopts its Judgment, Nicaragua requests the Court to appoint
                      such an expert who could advise the Parties in the implementation of the
                      Judgment.”
                 On behalf of the Government of Costa Rica,
                 in the Counter‑Memorial :
                         “For these reasons, and reserving the right to supplement, amplify or
                      amend the present submissions, Costa Rica requests the Court to dismiss
                      all of Nicaragua’s claims in this proceeding.”
                 in the Rejoinder :
                         “For these reasons, and reserving the right to supplement, amplify or
                      amend the present submissions, Costa Rica requests the Court to dismiss
                      all of Nicaragua’s claims in this proceeding.”
                   52. At the oral proceedings in the joined cases, the following submissions
                 were presented by the Parties in the Nicaragua v. Costa Rica case :
                 On behalf of the Government of Nicaragua,
                 at the hearing of 30 April 2015 :
                        “1. In accordance with Article 60 of the Rules and the reasons given
                      during the written and oral phase of the pleadings the Republic of Nicara-
                      gua respectfully requests the Court to adjudge and declare that, by its con-
                      duct, the Republic of Costa Rica has breached :
                       (i) its obligation not to violate the integrity of Nicaragua’s territory as
                           delimited by the 1858 Treaty of Limits as interpreted by the Cleveland
                           Award of 1888 and the five Awards of the Umpire E. P. Alexander of
                           30 September 1897, 20 December 1897, 22 March 1898, 26 July 1899,
                           and 10 March 1900 ;
                      (ii) its obligation not to damage Nicaraguan territory ;

                      (iii) its obligations under general international law and the relevant environ-
                            mental conventions, including the Ramsar Convention on Wetlands,
                            the Agreement over the Border Protected Areas between Nicaragua
                            and Costa Rica (International System of Protected Areas for
                            Peace [SI‑A‑PAZ] Agreement), the Convention on Biological Diver-
                            sity and the Convention for the Conservation of the Biodiversity and
                            Protection of the Main Wildlife Sites in Central America.

                        2. Nicaragua also requests the Court to adjudge and declare that
                      Costa Rica must :
                       (i) cease all its continuing internationally wrongful acts that affect or are
                           likely to affect the rights of Nicaragua ;

                                                                                28

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                      (ii) inasmuch as possible, restore the situation to the status quo ante, in full
                           respect of Nicaragua’s sovereignty over the San Juan de Nicaragua
                           River, including by taking the emergency measures necessary to allevi-
                           ate or mitigate the continuing harm being caused to the river and the
                           surrounding environment ;
                     (iii) compensate for all damages caused insofar as they are not made good
                           by restitution, including the costs added to the dredging of the San Juan
                           de Nicaragua River, with the amount of the compensation to be deter-
                           mined in a subsequent phase of the case.
                        3. Furthermore, Nicaragua requests the Court to adjudge and declare
                      that Costa Rica must :
                       (i) not undertake any future development in the area without an appro-
                           priate transboundary environmental impact assessment and that this
                           assessment must be presented in a timely fashion to Nicaragua for its
                           analysis and reaction ;
                      (ii) refrain from using Route 1856 to transport hazardous material as long
                           as it has not given the guarantees that the road complies with the best
                           construction practices and the highest regional and international stand-
                           ards of security for road traffic in similar situations.

                        4. The Republic of Nicaragua further requests the Court to adjudge and
                      declare that Nicaragua is entitled :
                       (i) in accordance with the 1858 Treaty as interpreted by the subsequent arbi-
                           tral awards, to execute works to improve navigation on the San Juan River
                           and that these works include the dredging of the San Juan de Nicaragua
                           River to remove sedimentation and other barriers to navigation.”
                 On behalf of the Government of Costa Rica,
                 at the hearing of 1 May 2015: “For the reasons set out in the written and oral
                 pleadings, Costa Rica requests the Court to dismiss all of Nicaragua’s claims in
                 this proceeding.”

                                                           *
                                                       *       *
                   53. The Court will begin by dealing with the elements common to both
                 cases. It will thus address, in a first part, the question of its jurisdiction,
                 before recalling, in a second part, the geographical and historical context
                 and the origin of the disputes.
                   The Court will then examine in turn, in two separate parts, the dis-
                 puted issues in the Costa Rica v. Nicaragua case and in the Nicaragua v.
                 Costa Rica case.

                                        I. Jurisdiction of the Court

                   54. With regard to the Costa Rica v. Nicaragua case, the Court recalls
                 that Costa Rica invokes, as bases of jurisdiction, Article XXXI of the
                 Pact of Bogotá and the declarations by which the Parties have recognized

                                                                                29

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                 the compulsory jurisdiction of the Court under paragraphs 2 and 5 of
                 Article 36 of the Statute (see paragraph 2 above). It notes that Nicaragua
                 does not contest its jurisdiction to entertain Costa Rica’s claims.

                   The Court finds that it has jurisdiction over the dispute.
                   55. With regard to the Nicaragua v. Costa Rica case, the Court notes
                 that Nicaragua invokes, for its part, as bases of jurisdiction, Article XXXI
                 of the Pact of Bogotá and the above‑mentioned declarations of accep-
                 tance (see paragraph 2 above). It further observes that Costa Rica does
                 not contest its jurisdiction to entertain Nicaragua’s claims.
                   The Court finds that it has jurisdiction over the dispute.

                               II. Geographical and Historical Context
                                      and Origin of the Disputes

                   56. The San Juan River runs approximately 205 km from Lake Nica-
                 ragua to the Caribbean Sea. At a point known as “Delta Colorado” (or
                 “Delta Costa Rica”), the San Juan River divides into two branches : the
                 Lower San Juan is the northerly of these two branches and flows into the
                 Caribbean Sea about 30 km downstream from the delta, near the town of
                 San Juan de Nicaragua, formerly known as San Juan del Norte or Grey-
                 town ; the Colorado River is the southerly and larger of the two branches
                 and runs entirely within Costa Rica, reaching the Caribbean Sea at Barra
                 de Colorado, about 20 km south‑east of the mouth of the Lower San
                 Juan. The Parties are in agreement that the Colorado River currently
                 receives approximately 90 per cent of the water of the San Juan River,
                 with the remaining 10 per cent flowing into the Lower San Juan.

                    57. The area situated between the Colorado River and the Lower San
                 Juan is broadly referred to as Isla Calero (approximately 150 sq km).
                 Within that area, there is a smaller region known to Costa Rica as Isla
                 Portillos and to Nicaragua as Harbor Head (approximately 17 sq km) ; it
                 is located north of the former Taura River. In the north of Isla Portillos
                 is a lagoon, called Laguna Los Portillos by Costa Rica and Harbor Head
                 Lagoon by Nicaragua. This lagoon is at present separated from the
                 Caribbean Sea by a sandbar (see sketch‑map No. 1 p. 692).

                    58. Isla Calero is part of the Humedal Caribe Noreste (Northeast Carib-
                 bean Wetland) which was designated by Costa Rica in 1996 as a wetland
                 of international importance under the Ramsar Convention. The area
                 immediately adjacent to it — including the San Juan River itself and a
                 strip of land 2 km in width abutting the river’s left (Nicaraguan) bank —
                 was designated by Nicaragua as a wetland of international importance
                 under the Ramsar Convention in 2001 and is known as the Refugio de
                 Vida Silvestre Río San Juan (San Juan River Wildlife Refuge).

                                                                                30

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5 Ord 1088.indb 59
                                                                                Sketch-map No. 1:
                                                                                Geographical context
                                          84°45’ W                                         84°30′W                     84°15′W                                        84°0′W                                               83°45′W                                                     83°30′W

                      11° 15’ N
                                                                                C A R I B B E A N
                                                                                S E A

                                                                                N IC A R AG UA                                                                                Harbor
                                                                                Head
                                   Lake                                                                                Lagoon

                                  Nicara-                                                                                N IC AR AGUA
                                   gua                                                                                Caño dredged
                                                                                Castillo Viejo                                                                                San Juan                           Punta de Castilla
                                                                                in 2010
                                                                                Marker II                                                                                de Nicaragua                       Isla Portillos
                                                                                CO STA                                                  former Taura River
                                                                                RIC A
                                                                                R i ve r

                     11° 0’ N
                                                                                Jua n

                                                                                Enlargement of the northern part of
                                                                                an
                                                                                rS

                                                                    CO STA              RI C A                                                          Isla Portillos and surrounding area                                                  e
                                                                                Lo w
                                                                                Delta Colorado                          Isla Calero

                                                                                er
                                                                                Boca San Carlos                    Sa
                                                                                n                      er
                                                                                - 31 -

                                                                                Riv
                                                                                Juan Riv

                                                                                to
                                                                                r
                                                                N                                                                                r

                                                                                ni
                                                                                Colorado

                                                                                ve
                                                                                ve
                                                                                i

                                  This sketch map has been prepared for illustrative purposes only

                                                                                Ri
                                                                                River

                                                                                ier
                                                                                s
                                             0                10              20km
                                                                                r   lo

                                                                                Inf
                                      Universal Transverse Mercator projection, zone 11N                                         Ca
                                                                                San

                     10° 45’ N
                                                        WGS84 Datum
                                                                                certain activities and construction of a road (judgment)

                                                                                Sarapiquí R
                                                                                692

                     31

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                       certain activities and construction of a road (judgment)         693

                    59. The present disputes between the Parties are set within a historical
                 context dating back to the 1850s. Following hostilities between the two
                 States in 1857, the Governments of Costa Rica and Nicaragua signed on
                 15 April 1858 a Treaty of Limits, which was ratified by Costa Rica on
                 16 April 1858 and by Nicaragua on 26 April 1858 (hereinafter the
                 “1858 Treaty”). The 1858 Treaty fixed the course of the boundary between
                 Costa Rica and Nicaragua from the Pacific Ocean to the Caribbean Sea.
                 According to Article II of the Treaty (quoted in paragraph 71 below),
                 part of the boundary between the two States runs along the right
                 (Costa Rican) bank of the San Juan River from a point three English
                 miles below Castillo Viejo, a small town in Nicaragua, to “the end of
                 Punta de Castilla, at the mouth of the San Juan” on the Caribbean coast.
                 Article VI of the 1858 Treaty (quoted in paragraph 133 below) estab-
                 lished Nicaragua’s dominium and imperium over the waters of the river,
                 but at the same time affirmed Costa Rica’s right of free navigation on the
                 river for the purposes of commerce.
                    60. Following challenges by Nicaragua on various occasions to the
                 validity of the 1858 Treaty, Costa Rica and Nicaragua signed another
                 instrument on 24 December 1886, whereby the two States agreed to sub-
                 mit the question of the validity of the 1858 Treaty to the President of the
                 United States, Grover Cleveland, for arbitration. In addition, the Parties
                 agreed that, if the 1858 Treaty were found to be valid, President Cleve-
                 land should also decide “upon all the other points of doubtful interpreta-
                 tion which either of the parties may find in the treaty”. On 22 June 1887,
                 Nicaragua communicated to Costa Rica 11 points of doubtful interpreta-
                 tion, which were subsequently submitted to President Cleveland for reso-
                 lution. The Cleveland Award of 1888 confirmed, in its paragraph 1, the
                 validity of the 1858 Treaty and found, in its paragraph 3 (1), that the
                 boundary line between the two States on the Atlantic side “begins at the
                 extremity of Punta de Castilla at the mouth of the San Juan de Nicaragua
                 River, as they both existed on the 15th day of April 1858”. The Cleveland
                 Award also settled the other points of doubtful interpretation submitted
                 by Nicaragua, such as the conditions under which Nicaragua may carry
                 out works of improvement on the San Juan River (para. 3 (6), quoted in
                 paragraph 116 below), the conditions under which Costa Rica may pre-
                 vent Nicaragua from diverting the waters of the San Juan (para. 3 (9),
                 quoted in paragraph 116 below), and the requirement that Nicaragua not
                 make any grants for the purpose of constructing a canal across its terri-
                 tory without first asking for the opinion of Costa Rica (para. 3 (10)) or,
                 “where the construction of the canal will involve an injury to the natural
                 rights of Costa Rica”, obtaining its consent (para. 3 (11)).

                   61. Subsequent to the Cleveland Award, Costa Rica and Nicaragua
                 agreed in 1896, under the Pacheco‑Matus Convention on border demar-
                 cation, to establish two national Demarcation Commissions, each com-

                                                                                32

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                 posed of two members (Art. I). The Pacheco‑Matus Convention further
                 provided that the Commissions would include an engineer, appointed by
                 the President of the United States of America, who “shall have broad
                 powers to decide whatever kind of differences may arise in the course of
                 any operations and his ruling shall be final” (Art. II). United States Gen-
                 eral Edward Porter Alexander was so appointed. During the demarcation
                 process, which began in 1897 and was concluded in 1900, General Alex-
                 ander rendered five awards, the first three of which are of particular rel-
                 evance to the Costa Rica v. Nicaragua case (see paragraphs 73‑75 below).

                    62. Starting in the 1980s, some disagreements arose between Costa Rica
                 and Nicaragua concerning the precise scope of Costa Rica’s rights of
                 navigation under the 1858 Treaty. This dispute led Costa Rica to file an
                 Application with the Court instituting proceedings against Nicaragua on
                 29 September 2005. The Court rendered its Judgment on 13 July 2009,
                 which, inter alia, clarified Costa Rica’s navigational rights and the extent
                 of Nicaragua’s power to regulate navigation on the San Juan River (Dis‑
                 pute regarding Navigational and Related Rights (Costa Rica v. Nicara‑
                 gua), Judgment, I.C.J. Reports 2009, p. 213).
                    63. On 18 October 2010, Nicaragua started dredging the San Juan
                 River in order to improve its navigability. It also carried out works in the
                 northern part of Isla Portillos (see sketch‑map No. 1 p. 692). In this
                 regard, Costa Rica contends that Nicaragua artificially created a channel
                 (both Parties refer to such channels as “caños”) on Costa Rican territory,
                 in Isla Portillos between the San Juan River and Laguna Los Portillos/
                 Harbor Head Lagoon, whereas Nicaragua argues that it was only clear-
                 ing an existing caño on Nicaraguan territory. Nicaragua also sent some
                 military units and other personnel to that area. On 18 November 2010,
                 Costa Rica filed its Application instituting proceedings in the Costa Rica v.
                 Nicaragua case (see paragraph 1 above). Costa Rica also submitted a
                 request for the indication of provisional measures under Article 41 of the
                 Statute (see paragraph 3 above).
                    64. In December 2010, Costa Rica started works for the construction of
                 Route 1856 Juan Rafael Mora Porras (hereinafter the “road”), which runs
                 in Costa Rican territory along part of its border with Nicaragua. The
                 road has a planned length of 159.7 km, extending from Los Chiles in the
                 west to a point just beyond “Delta Colorado” in the east. For 108.2 km,
                 it follows the course of the San Juan River (see sketch‑map No. 2
                 p. 695). On 21 February 2011, Costa Rica adopted an Executive Decree
                 declaring a state of emergency in the border area, which Costa Rica
                 maintains exempted it from the obligation to conduct an environmental
                 impact assessment before constructing the road. On 22 December 2011,
                 Nicaragua filed its Application instituting proceedings in the Nicaragua v.
                 Costa Rica case (see paragraph 9 above), claiming in particular that the
                 construction of the road resulted in significant transboundary harm.

                                                                                33

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5 Ord 1088.indb 65
                                                                                Sketch-map No. 2:
                                                                                Route 1856 Juan Rafael Mora Porras
                                          84°45’ W                                         84°30′W                                            84°15′W                                        84°0′W                                           83°45′W                                                     83°30′W

                      11° 15’ N
                                                                                C A R I B B E A N
                                                                                S E A

                                                                                N IC A R AG UA
                                   Lake
                                  Nicara-
                                   gua
                                                                                Castillo Viejo                                                                                San Juan                           Punta de Castilla
                                                                                Marker II                                                                                de Nicaragua                       Isla Portillos
                                                     Los Chiles                              R o                                                                                former Taura River
                                                                                u t
                                                                                e
                                                                                R i ve r

                     11° 0’ N
                                                                                1 8
                                                                                Jua n

                                                                                5
                                                                                6
                                                                                an
                                                                                rS

                                                                                e
                                                                                J u
                                                                    CO S TA             RI C A                                        a                                                                                Lo w
                                                                                n                                                                                Delta Colorado                          Isla Calero
                                                                                R

                                                                                er
                                                                                a                       Boca San Carlos                    Sa
                                                                                n                  er
                                                                                - 34 -

                                                                                f a

                                                                                Riv
                                                                                Juan Riv
                                                                                e l
                                                                                M o

                                                                                to
                                                                                r a

                                                                                r
                                                                N                                                                                P o r r a s
                                                                                r

                                                                                ni
                                                                                Colorado

                                                                                ve
                                                                                ve
                                                                                i

                                  This sketch map has been prepared for illustrative purposes only

                                                                                Ri
                                                                                River

                                                                                ier
                                                                                s
                                             0                10              20km
                                                                                o
                                                                                rl

                                                                                Inf
                                      Universal Transverse Mercator projection, zone 11N                                                               Ca
                                                                                San
                                                                                certain activities and construction of a road (judgment)

                     10° 45’ N
                                                        WGS84 Datum
                                                                                Sarapiquí R
                                                                                695

                     34

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                       certain activities and construction of a road (judgment)           696

                               III. Issues in the Costa Rica v. Nicaragua Case

                                  A. Sovereignty over the Disputed Territory
                                        and Alleged Breaches Thereof
                     65. Costa Rica submits that Nicaragua breached
                       “the obligation to respect the sovereignty and territorial integrity of
                       the Republic of Costa Rica, within the boundaries delimited by the
                       1858 Treaty of Limits and further defined by the Demarcation Com-
                       mission established by the Pacheco‑Matus Convention, in particular
                       by the first and second Alexander Awards” (final submissions,
                       para. 2 (b) (i)).
                 This claim is based on the premise that “[s]overeignty over the ‘disputed
                 territory’, as defined by the Court in its Orders of 8 March 2011 and
                 22 November 2013, belongs to the Republic of Costa Rica” (ibid.,
                 para. 2 (a)). In its final submissions Costa Rica requested the Court to
                 make a finding also on the issue of sovereignty over the disputed terri-
                 tory.
                    66. Costa Rica alleges that Nicaragua violated its territorial sover-
                 eignty in the area of Isla Portillos in particular by excavating in 2010 a
                 caño with the aim of connecting the San Juan River with the Harbor
                 Head Lagoon and laying claim to Costa Rican territory. According to
                 Costa Rica, this violation of sovereignty was exacerbated by Nicaragua’s
                 establishment of a military presence in the area and by its excavation in
                 2013 of two other caños located near the northern tip of Isla Portillos.

                    67. The Court notes that although the violations that allegedly took
                 place in 2013 occurred after the Application was made, they concern facts
                 which are of the same nature as those covered in the Application and
                 which the Parties had the opportunity to discuss in their pleadings. These
                 alleged violations may therefore be examined by the Court as part of the
                 merits of the claim. They will later also be considered in relation to Nica-
                 ragua’s compliance with the Court’s Order on provisional measures of
                 8 March 2011.
                    68. Nicaragua does not contest that it dredged the three caños, but
                 maintains that “Nicaragua enjoys full sovereignty over the caño joining
                 Harbor Head Lagoon with the San Juan River proper, the right bank of
                 which constitutes the land boundary as established by the 1858 Treaty as
                 interpreted by the Cleveland and Alexander Awards” (final submissions,
                 para. (b) (i)). Nicaragua further submits that “Costa Rica is under an
                 obligation to respect the sovereignty and territorial integrity of Nicara-
                 gua, within the boundaries delimited by the 1858 Treaty of Limits as
                 interpreted by the Cleveland and Alexander Awards” (ibid., para. (b) (ii)).
                    69. Since it is uncontested that Nicaragua conducted certain activities
                 in the disputed territory, it is necessary, in order to establish whether
                 there was a breach of Costa Rica’s territorial sovereignty, to determine

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                 which State has sovereignty over that territory. The “disputed territory”
                 was defined by the Court in its Order of 8 March 2011 on provisional
                 measures as “the northern part of Isla Portillos, that is to say, the area of
                 wetland of some 3 square kilometres between the right bank of the dis-
                 puted caño, the right bank of the San Juan River up to its mouth at the
                 Caribbean Sea and the Harbor Head Lagoon” (I.C.J. Reports 2011 (I),
                 p. 19, para. 55). The caño referred to is the one which was dredged by
                 Nicaragua in 2010. Nicaragua did not contest this definition of the “dis-
                 puted territory”, while Costa Rica expressly endorsed it in its final sub-
                 missions (para. 2 (a)). The Court will maintain the definition of “disputed
                 territory” given in the 2011 Order. It recalls that its Order of 22 Novem-
                 ber 2013 indicating provisional measures specified that a Nicaraguan
                 military encampment “located on the beach and close to the line of veg-
                 etation” near one of the caños dredged in 2013 was “situated in the dis-
                 puted territory as defined by the Court in its Order of 8 March 2011”
                 (I.C.J. Reports 2013, p. 365, para. 46).

                    70. The above definition of the “disputed territory” does not specifi-
                 cally refer to the stretch of coast abutting the Caribbean Sea which lies
                 between the Harbor Head Lagoon, which lagoon both Parties agree is
                 Nicaraguan, and the mouth of the San Juan River. In their oral argu-
                 ments the Parties expressed different views on this issue. However, they
                 did not address the question of the precise location of the mouth of the
                 river nor did they provide detailed information concerning the coast. Nei-
                 ther Party requested the Court to define the boundary more precisely with
                 regard to this coast. Accordingly, the Court will refrain from doing so.
                    71. In their claims over the disputed territory both Parties rely on the
                 1858 Treaty, the Cleveland Award and the Alexander Awards. According
                 to Article II of the Treaty :
                          “The dividing line between the two Republics, starting from the
                       Northern Sea, shall begin at the end of Punta de Castilla, at the mouth
                       of the San Juan de Nicaragua River, and shall run along the right bank
                       of the said river up to a point three English miles distant from Castillo
                       Viejo . . .” [In the Spanish original: “La línea divisoria de las dos Repú‑
                       blicas, partiendo del mar del Norte, comenzará en la extremidad de
                       Punta de Castilla, en la desembocadura del río de San Juan de Nicara‑
                       gua, y continuará marcándose con la márgen derecha del expresado río,
                       hasta un punto distante del Castillo Viejo tres millas inglesas . . .”]
                     72. In 1888 President Cleveland found in his Award that :

                          “The boundary line between the Republics of Costa Rica and Nic-
                       aragua, on the Atlantic side, begins at the extremity of Punta de Cas-
                       tilla at the mouth of the San Juan de Nicaragua River, as they both
                       existed on the 15th day of April 1858. The ownership of any accretion
                       to said Punta de Castilla is to be governed by the laws applicable to

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                     that subject.” (United Nations, Reports of International Arbitral
                     Awards (RIAA), Vol. XXVIII, p. 209.)
                   73. When the Commissions on demarcation were established by the
                 Pacheco‑Matus Convention, one member, to be designated by the Presi-
                 dent of the United States of America, was given the power to “resolve
                 any dispute between the Commissions of Costa Rica and Nicaragua aris-
                 ing from the operations” (see paragraph 61 above). According to this
                 Convention, the said person “shall have broad powers to decide whatever
                 kind of differences may arise in the course of any operations and his rul-
                 ing shall be final” (Art. II, RIAA, Vol. XXVIII, p. 212). On this basis,
                 General Alexander, who had been duly designated to this position, ren-
                 dered five awards concerning the border. In his first Award he stated that
                 the boundary line :

                     “must follow the . . . branch . . . called the Lower San Juan, through
                     its harbor and into the sea.
                        The natural terminus of that line is the right‑hand headland of the
                     harbor mouth.” (Ibid., p. 217.)
                 He observed that :
                     “throughout the treaty the river is treated and regarded as an outlet
                     of commerce. This implies that it is to be considered as in average
                     condition of water, in which condition alone it is navigable.” (Ibid.,
                     pp. 218‑219.)
                 He then defined the initial part of the boundary starting from the Carib-
                 bean Sea in the following terms :
                        “The exact spot which was the extremity of the headland of Punta
                     de Castillo [on] April 15, 1858, has long been swept over by the Car-
                     ibbean Sea, and there is too little concurrence in the shore outline of
                     the old maps to permit any certainty of statement of distance or exact
                     direction to it from the present headland. It was somewhere to the
                     north-eastward, and probably between 600 and 1,600 feet distant, but
                     it can not now be certainly located. Under these circumstances it best
                     fulfils the demands of the treaty and of President Cleveland’s award
                     to adopt what is practically the headland of today, or the north-
                     western extremity of what seems to be the solid land, on the east side
                     of Harbor Head Lagoon.

                        I have accordingly made personal inspection of this ground, and
                     declare the initial line of the boundary to run as follows, to wit :
                        Its direction shall be due north-east and south-west, across the bank
                     of sand, from the Caribbean Sea into the waters of Harbor Head
                     Lagoon. It shall pass, at its nearest point, 300 feet on the north-west
                     side from the small hut now standing in that vicinity. On reaching the
                     waters of Harbor Head Lagoon the boundary line shall turn to the

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                     left, or south-eastward, and shall follow the water’s edge around the
                     harbor until it reaches the river proper by the first channel met. Up
                     this channel, and up the river proper, the line shall continue to ascend
                     as directed in the treaty.” (RIAA, Vol. XXVIII, p. 220.)

                 A sketch illustrating this initial part of the boundary in the geographic
                 situation prevailing at the time was attached to this first Award (ibid.,
                 p. 221). In that sketch, what the Arbitrator considered to be the “first
                 channel” was the branch of the Lower San Juan River which was then
                 flowing into the Harbor Head Lagoon (see sketch‑map No. 3 below). The
                 same boundary line was sketched with greater precision in the proceed-
                 ings of the Commissions on demarcation.

                    74. The second Alexander Award envisaged the possibility that the
                 banks of the San Juan River would “not only gradually expand or con-
                 tract but that there [would] be wholesale changes in its channels”. The
                 Arbitrator observed that :
                        “Today’s boundary line must necessarily be affected in future by
                     all these gradual or sudden changes. But the impact in each case can
                     only be determined by the circumstances of the case itself, on a
                     case‑by‑case basis in accordance with such principles of international
                     law as may be applicable.
                        The proposed measurement and demarcation of the boundary line
                     will not have any effect on the application of those principles.” (RIAA,
                     Vol. XXVIII, p. 224.)

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                    75. In his third Award, General Alexander noted that “borders delim-
                 ited by waterways are likely to change when changes occur in the beds of
                 such waterways. In other words, it is the riverbed that affects changes and
                 not the water within, over or below its banks.” (RIAA, Vol. XXVIII,
                 p. 229.) He reached the following conclusion :

                        “Let me sum up briefly and provide a clearer understanding of the
                     entire question in accordance with the principles set out in my first
                     award, to wit, that in the practical interpretation of the 1858 Treaty,
                     the San Juan River must be considered a navigable river. I therefore
                     rule that the exact dividing line between the jurisdictions of the two
                     countries is the right bank of the river, with the water at ordinary
                     stage and navigable by ships and general‑purpose boats. At that stage,
                     every portion of the waters of the river is under Nicaraguan jurisdic-
                     tion. Every portion of land on the right bank is under Costa Rican
                     jurisdiction.” (Ibid., p. 230.)

                    76. The Court considers that the 1858 Treaty and the awards by Presi-
                 dent Cleveland and General Alexander lead to the conclusion that Arti-
                 cle II of the 1858 Treaty, which places the boundary on the “right bank
                 of the . . . river”, must be interpreted in the context of Article VI (quoted
                 in full at paragraph 133 below), which provides that “the Republic of
                 Costa Rica shall . . . have a perpetual right of free navigation on the . . .
                 waters [of the river] between [its] mouth . . . and a point located three
                 English miles below Castillo Viejo”. As General Alexander observed in
                 demarcating the boundary, the 1858 Treaty regards the river, “in average
                 condition of water”, as an “outlet of commerce” (see paragraph 73
                 above). In the view of the Court, Articles II and VI, taken together, pro-
                 vide that the right bank of a channel of the river forms the boundary on
                 the assumption that this channel is a navigable “outlet of commerce”.
                 Thus, Costa Rica’s rights of navigation are linked with sovereignty over
                 the right bank, which has clearly been attributed to Costa Rica as far as
                 the mouth of the river.

                    77. Costa Rica contends that, while no channel of the San Juan River
                 now flows into the Harbor Head Lagoon, there has been no significant
                 shifting of the bed of the main channel of the Lower San Juan River since
                 the Alexander Awards. Costa Rica maintains that the territory on the
                 right bank of that channel as far as the river’s mouth in the Caribbean
                 Sea should be regarded as under Costa Rican sovereignty. According to
                 Costa Rica, no importance should be given to what it considers to be an
                 artificial caño which was excavated by Nicaragua in 2010 in order to con-
                 nect the San Juan River with the Harbor Head Lagoon.
                    78. Nicaragua argues that, as a result of natural modifications in the
                 geographical configuration of the disputed territory, the “first channel” to
                 which General Alexander referred in his first Award is now a channel

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                 connecting the river, at a point south of the Harbor Head Lagoon, with
                 the southern tip of that lagoon. The channel in question, according to
                 Nicaragua, is the caño that it dredged in 2010 only to improve its naviga-
                 bility. Relying on the alleged existence of this caño over a number of years
                 and contending that it now marks the boundary, Nicaragua claims sover-
                 eignty over the whole of the disputed territory.
                    79. According to Nicaragua, the existence of the caño before 2010 is
                 confirmed by aerial and satellite imagery. In particular, Nicaragua alleges
                 that a satellite picture dating from 1961 shows that a caño existed where
                 Nicaragua was dredging in 2010.
                    80. Costa Rica points out that, especially by reason of the thick vege-
                 tation, aerial and satellite images of the disputed territory are not clear,
                 including the satellite picture of 1961. Moreover, Costa Rica produces a
                 satellite image dating from August 2010, which would rule out the exis-
                 tence of a channel in the period between the clearing of vegetation in the
                 location of the caño and the dredging of the caño. In the oral proceedings,
                 Nicaragua admitted that because of the tree canopy, only an inspection
                 on the ground could provide certainty regarding the caño.
                    81. In the opinion of the Court, an inspection would hardly be useful
                 for reconstructing the situation prevailing before 2010. The Court consid-
                 ers that, given the general lack of clarity of satellite and aerial images and
                 the fact that the channels that may be identified on such images do not
                 correspond to the location of the caño dredged in 2010, this evidence is
                 insufficient to prove that a natural channel linked the San Juan River
                 with the Harbor Head Lagoon following the same course as the caño that
                 was dredged.
                    82. In order further to substantiate the view that the caño had existed
                 for some time before it was dredged, Nicaragua also supplies three affida-
                 vits of Nicaraguan policemen or military agents who refer to a stream
                 linking the San Juan River with the lagoon and assert that it was navi-
                 gable for part of the year. Some affidavits of other agents mention streams
                 in the area of the lagoon and describe them as navigable by boats to a
                 certain extent, but do not specify their location.

                    83. The Court recalls that “[i]n determining the evidential weight of
                 any statement by an individual, the Court necessarily takes into account
                 its form and the circumstances in which it was made” (Application of the
                 Convention on the Prevention and Punishment of the Crime of Genocide
                 (Croatia v. Serbia), Judgment, I.C.J. Reports 2015 (I), p. 78, para. 196).
                 Affidavits will be treated “with caution”, in particular those made by
                 State officials for purposes of litigation (ibid., pp. 78, paras. 196‑197,
                 referring to Territorial and Maritime Dispute between Nicaragua and Hon‑
                 duras in the Caribbean Sea (Nicaragua v. Honduras), Judgment,
                 I.C.J. Reports 2007 (II), p. 731, para. 244). In the present case, the Court
                 finds that the affidavits of Nicaraguan State officials, which were prepared
                 after the institution of proceedings by Costa Rica, provide little support
                 for Nicaragua’s contention.

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                    84. Nicaragua refers to a map produced in 1949 by the National Geo-
                 graphic Institute of Costa Rica which shows a caño in the location of the
                 one dredged in 2010. It acknowledges, however, that the map in question
                 describes the entire disputed territory as being under Costa Rican sover-
                 eignty. Nicaragua further invokes a map published in 1971 by the same
                 Institute which shows a boundary close to the line claimed by Nicaragua.
                 However, the Court notes that this evidence is contradicted by several
                 official maps of Nicaragua, in particular a map of 1967 of the Directorate
                 of Cartography and a map, dating from 2003, published by the Nicara-
                 guan Institute of Territorial Studies (INETER, by its Spanish acronym),
                 which depict the disputed area as being under Costa Rica’s sovereignty.

                    85. As the Boundary Commission in the Eritrea/Ethiopia case stated,
                 in a passage that was quoted with approval by the Court in the case con-
                 cerning Sovereignty over Pedra Branca/Pulau Batu Puteh, Middle Rocks
                 and South Ledge (Malaysia/Singapore), a map “stands as a statement of
                 geographical fact, especially when the State adversely affected has itself
                 produced and disseminated it, even against its own interest” (Judgment,
                 I.C.J. Reports 2008, p. 95, para. 271). In the present case, the evidence of
                 maps published by the Parties on the whole gives support to Costa Rica’s
                 position, but their significance is limited, given that they are all small‑scale
                 maps which are not focused on the details of the disputed territory.

                    86. Both Parties invoke effectivités to corroborate their claims to ter-
                 ritorial sovereignty. Costa Rica argues that it had exercised sovereignty
                 over the disputed territory without being challenged by Nicaragua until
                 2010. Costa Rica recalls that it adopted legislation applying specifically to
                 that area, that it issued permits or titles to use land in the same territory,
                 and that Isla Portillos was included within the area it designated as a
                 wetland of international importance under the Ramsar Convention
                 (Humedal Caribe Noreste). Costa Rica notes that, when Nicaragua regis-
                 tered its own wetland of international importance concerning the area
                 (Refugio de Vida Silvestre Río San Juan), it only included the Harbor
                 Head Lagoon and did not encompass the disputed territory.

                   87. Nicaragua for its part contends that it acted as sovereign over the
                 disputed territory. Relying on affidavits by State officials and two police
                 reports, it asserts that at least since the late 1970s the Nicaraguan army,
                 navy and police have all patrolled the area in and around Harbor Head
                 Lagoon, including the caños connecting the lagoon with the San Juan
                 River.
                   88. Costa Rica questions the value of the evidence adduced by Nicara-
                 gua to substantiate its claim of having exercised sovereign powers in the
                 disputed territory.

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                    Nicaragua argues that Costa Rica’s claimed exercise of sovereignty was
                 merely a limited “paper presence” in the disputed territory not supported
                 by any actual conduct on the ground.
                    89. The effectivités invoked by the Parties, which the Court considers
                 are in any event of limited significance, cannot affect the title to sover-
                 eignty resulting from the 1858 Treaty and the Cleveland and Alexander
                 Awards.
                    90. The Court notes that the existence over a significant span of time
                 of a navigable caño in the location claimed by Nicaragua is put into ques-
                 tion by the fact that in the bed of the channel there were trees of consider-
                 able size and age which had been cleared by Nicaragua in 2010. Moreover,
                 as was noted by Costa Rica’s main expert, if the channel had been a dis-
                 tributary of the San Juan River, “sediment would have filled in, or at a
                 minimum partially‑filled, the southern part of the lagoon”. Furthermore,
                 the fact that, as the Parties’ experts agree, the caño dredged in 2010 no
                 longer connected the river with the lagoon by mid‑summer 2011 casts
                 doubt on the existence over a number of years of a navigable channel fol-
                 lowing the same course before Nicaragua carried out its dredging activi-
                 ties. This caño could hardly have been the navigable outlet of commerce
                 referred to above (see paragraph 76).
                    91. If Nicaragua’s claim were accepted, Costa Rica would be prevented
                 from enjoying territorial sovereignty over the right bank of the San Juan
                 River as far as its mouth, contrary to what is stated in the 1858 Treaty
                 and in the Cleveland Award. Moreover, according to Article VI of the
                 1858 Treaty (quoted below at paragraph 133), Costa Rica’s rights of nav-
                 igation are over the waters of the river, the right bank of which forms the
                 boundary between the two countries. As the Court noted (see para-
                 graph 76 above), these rights of navigation are linked with sovereignty
                 over the right bank.
                    92. The Court therefore concludes that the right bank of the caño
                 which Nicaragua dredged in 2010 is not part of the boundary between
                 Costa Rica and Nicaragua, and that the territory under Costa Rica’s sov-
                 ereignty extends to the right bank of the Lower San Juan River as far as
                 its mouth in the Caribbean Sea. Sovereignty over the disputed territory
                 thus belongs to Costa Rica.
                    93. It is not contested that Nicaragua carried out various activities in
                 the disputed territory since 2010, including excavating three caños and
                 establishing a military presence in parts of that territory. These activities
                 were in breach of Costa Rica’s territorial sovereignty. Nicaragua is
                 responsible for these breaches and consequently incurs the obligation to
                 make reparation for the damage caused by its unlawful activities (see Sec-
                 tion E).
                    94. Costa Rica submits that “by occupying and claiming Costa Rican
                 territory” Nicaragua also committed other breaches of its obligations.

                   95. Costa Rica’s final submission 2 (b) (iv) asks the Court to adjudge
                 and declare that Nicaragua breached its obligation “not to use the San

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                 Juan River to carry out hostile acts” under Article IX of the 1858 Treaty.
                 This provision reads as follows :
                        “Under no circumstances, and even in [the] case that the Republics
                     of Costa Rica and Nicaragua should unhappily find themselves in a
                     state of war, neither of them shall be allowed to commit any act of
                     hostility against the other, whether in the port of San Juan del Norte,
                     or in the San Juan River, or the Lake of Nicaragua.” [In the Spanish
                     original: “Por ningún motivo, ni en caso y estado de guerra, en que por
                     desgracia llegasen á encontrarse las Repúblicas de Nicaragua y
                     Costa Rica, les será permitido ejercer ningún acto de hostilidad entre
                     ellas en el puerto de San Juan del Norte, ni en el río de este nombre y
                     Lago de Nicaragua.”]
                 No evidence of hostilities in the San Juan River has been provided. There-
                 fore the submission concerning the breach of Nicaragua’s obligations
                 under Article IX of the Treaty must be rejected.

                   96. In its final submission 2 (b) (ii), Costa Rica asks the Court to find
                 a breach by Nicaragua of “the prohibition of the threat or use of force
                 under Article 2 (4) of the Charter of the United Nations and Article 22 of
                 the Charter of the Organization of American States”.

                    97. The relevant conduct of Nicaragua has already been addressed in
                 the context of the Court’s examination of the violation of Costa Rica’s
                 territorial sovereignty. The fact that Nicaragua considered that its activi-
                 ties were taking place on its own territory does not exclude the possibility
                 of characterizing them as an unlawful use of force. This raises the issue of
                 their compatibility with both the United Nations Charter and the Charter
                 of the Organization of American States. However, in the circumstances,
                 given that the unlawful character of these activities has already been
                 established, the Court need not dwell any further on this submission. As
                 in the case concerning Land and Maritime Boundary between Cameroon
                 and Nigeria (Cameroon v. Nigeria : Equatorial Guinea intervening), the
                 Court finds that, “by the very fact of the present Judgment and of the
                 evacuation” of the disputed territory, the injury suffered by Costa Rica
                 “will in all events have been sufficiently addressed” (Judgment,
                 I.C.J. Reports 2002, p. 452, para. 319).
                    98. In its final submission 2 (b) (iii), Costa Rica requests the Court to
                 find that Nicaragua made the territory of Costa Rica “the object, even
                 temporarily, of military occupation, contrary to Article 21 of the Charter
                 of the Organization of American States”. The first sentence of this provi-
                 sion stipulates: “The territory of a State is inviolable ; it may not be the
                 object, even temporarily, of military occupation or of other measures of
                 force taken by another State, directly or indirectly, on any grounds what-
                 ever.”
                    In order to substantiate this claim, Costa Rica refers to the presence of
                 military personnel of Nicaragua in the disputed territory.

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                    99. The Court has already established that the presence of military per-
                 sonnel of Nicaragua in the disputed territory was unlawful because it vio-
                 lated Costa Rica’s territorial sovereignty. The Court does not need to
                 ascertain whether this conduct of Nicaragua constitutes a military occu-
                 pation in breach of Article 21 of the Charter of the Organization of
                 American States.

                          B. Alleged Violations of International Environmental Law
                   100. The Court will now turn to Costa Rica’s allegations concerning
                 violations by Nicaragua of its obligations under international environ-
                 mental law in connection with its dredging activities to improve the navi-
                 gability of the Lower San Juan River. Costa Rica’s environmental claims
                 can be grouped into two broad categories. First, according to Costa Rica,
                 Nicaragua breached the procedural obligations to carry out an appropri-
                 ate transboundary environmental impact assessment of its dredging
                 works, and to notify, and consult with, Costa Rica regarding those works.
                 Secondly, Costa Rica alleges that Nicaragua breached the substantive
                 environmental obligation not to cause harm to Costa Rica’s territory.
                 The Court will consider Costa Rica’s allegations in turn.

                 1. Procedural obligations
                         The alleged breach of the obligation to carry out an environmental
                     (a)
                         impact assessment
                    101. The Parties broadly agree on the existence in general international
                 law of an obligation to conduct an environmental impact assessment con-
                 cerning activities carried out within a State’s jurisdiction that risk causing
                 significant harm to other States, particularly in areas or regions of shared
                 environmental conditions.

                   102. Costa Rica claims that Nicaragua has not complied with that
                 obligation, and must do so in advance of any further dredging. It submits
                 in particular that the analysis carried out in the Environmental Impact
                 Study undertaken by Nicaragua in 2006 does not support the conclusion
                 that the dredging project would cause no harm to the flow of the Colo-
                 rado River. Moreover, according to Costa Rica, the Environmental
                 Impact Study did not assess the impact of the dredging programme on
                 the wetlands. Costa Rica maintains that the artificial changes to the mor-
                 phology of the river resulting from Nicaragua’s dredging activities risked
                 causing an adverse impact on those wetlands. Costa Rica also argues that
                 a document entitled “Report : Ramsar Advisory Mission No. 72”, pre-
                 pared in April 2011, confirms the existence of a risk of transboundary

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                 harm, shows that Nicaragua’s study did not contain an assessment of that
                 risk, and concludes that such an assessment should have been undertaken
                 prior to the implementation of the dredging programme.
                    103. Nicaragua contends for its part that its 2006 Environmental
                 Impact Study and the related documentation fully addressed the potential
                 transboundary impact of its dredging programme, including its effects on
                 the environment of Costa Rica and the possible reduction in flow of the
                 Colorado River. It points out that this study concluded that the pro-
                 gramme posed no risk of significant transboundary harm and would actu-
                 ally have beneficial effects for the San Juan River and the surrounding
                 area. As to the document entitled “Report : Ramsar Advisory Mission
                 No. 72”, Nicaragua argues that it was only a draft report, on which Nica-
                 ragua commented in a timely manner, but which the Ramsar Secretariat
                 never finalized ; accordingly, it should be given no weight. Furthermore,
                 Nicaragua explains that the report’s conclusion that there had been no
                 analysis of the impact of the dredging programme on the hydrology of
                 the area was incorrect, as Nicaragua pointed out in the comments it sub-
                 mitted to the Ramsar Secretariat.

                                                       *
                   104. As the Court has had occasion to emphasize in its Judgment in
                 the case concerning Pulp Mills on the River Uruguay (Argentina v. Uru‑
                 guay) :
                      “the principle of prevention, as a customary rule, has its origins in the
                      due diligence that is required of a State in its territory. It is ‘every
                      State’s obligation not to allow knowingly its territory to be used for
                      acts contrary to the rights of other States’ (Corfu Channel (United
                      Kingdom v. Albania), Merits, Judgment, I.C.J. Reports 1949, p. 22).
                      A State is thus obliged to use all the means at its disposal in order to
                      avoid activities which take place in its territory, or in any area under
                      its jurisdiction, causing significant damage to the environment of
                      another State.” (Judgment, I.C.J. Reports 2010 (I), pp. 55‑56,
                      para. 101.)
                 Furthermore, the Court concluded in that case that “it may now be consid-
                 ered a requirement under general international law to undertake an envir
                 onmental impact assessment where there is a risk that the proposed
                 industrial activity may have a significant adverse impact in a transbound-
                 ary context, in particular, on a shared resource” (ibid., p. 83, para. 204).
                 Although the Court’s statement in the Pulp Mills case refers to industrial
                 activities, the underlying principle applies generally to proposed activities
                 which may have a significant adverse impact in a transboundary context.
                 Thus, to fulfil its obligation to exercise due diligence in preventing signifi-
                 cant transboundary environmental harm, a State must, before embarking
                 on an activity having the potential adversely to affect the environment of

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                 another State, ascertain if there is a risk of significant transboundary
                 harm, which would trigger the requirement to carry out an environmental
                 impact assessment.

                   Determination of the content of the environmental impact assessment
                 should be made in light of the specific circumstances of each case. As the
                 Court held in the Pulp Mills case :
                       “it is for each State to determine in its domestic legislation or in the
                       authorization process for the project, the specific content of the envir
                       onmental impact assessment required in each case, having regard to
                       the nature and magnitude of the proposed development and its likely
                       adverse impact on the environment as well as to the need to exercise
                       due diligence in conducting such an assessment” (I.C.J. Reports
                       2010 (I), p. 83, para. 205).
                 If the environmental impact assessment confirms that there is a risk of sig-
                 nificant transboundary harm, the State planning to undertake the activity
                 is required, in conformity with its due diligence obligation, to notify and
                 consult in good faith with the potentially affected State, where that is neces-
                 sary to determine the appropriate measures to prevent or mitigate that risk.
                    105. The Court notes that the risk to the wetlands alleged by Costa Rica
                 refers to Nicaragua’s dredging activities as a whole, including the dredg-
                 ing of the 2010 caño. The Court recalls that the dredging activities carried
                 out in breach of Costa Rica’s territorial sovereignty have been considered
                 previously. Accordingly, the Court will confine its analysis to ascertaining
                 whether Nicaragua’s dredging activities in the Lower San Juan carried a
                 risk of significant transboundary harm. The principal risk cited by
                 Costa Rica was the potential adverse impact of those dredging activities
                 on the flow of the Colorado River, which could also adversely affect
                 Costa Rica’s wetland. In 2006, Nicaragua conducted a study of the impact
                 that the dredging programme would have on its own environment, which
                 also stated that the programme would not have a significant impact on
                 the flow of the Colorado River. This conclusion was later confirmed by
                 both Parties’ experts. Having examined the evidence in the case file,
                 including the reports submitted and testimony given by experts called by
                 both Parties, the Court finds that the dredging programme planned in
                 2006 was not such as to give rise to a risk of significant transboundary
                 harm, either with respect to the flow of the Colorado River or to
                 Costa Rica’s wetland. In light of the absence of risk of significant trans-
                 boundary harm, Nicaragua was not required to carry out an environmen-
                 tal impact assessment.
                     (b) The alleged breach of an obligation to notify and consult

                   106. The Parties concur on the existence in general international law of
                 an obligation to notify, and consult with, the potentially affected State in

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                 respect of activities which carry a risk of significant transboundary harm.
                 Costa Rica contends that, in addition to its obligations under general
                 international law, Nicaragua was under a duty to notify and consult with
                 it as a result of treaty obligations binding on the Parties. First, it asserts
                 that Article 3, paragraph 2, and Article 5 of the Ramsar Convention pro-
                 vide for a duty to notify and consult. Secondly, it submits that Arti-
                 cles 13 (g) and 33 of the Convention for the Conservation of the
                 Biodiversity and Protection of Priority Wilderness Areas in Central
                 America establish an obligation to share information related to activities
                 which may be particularly damaging to biological resources.

                    107. While not contesting the existence of an obligation to notify and
                 consult under general international law, Nicaragua asserts that in the
                 present case such obligation is limited by the 1858 Treaty, as interpreted
                 by the Cleveland Award, which constitutes the lex specialis with respect
                 to procedural obligations. For Nicaragua, since the 1858 Treaty contains
                 no duty to notify or consult with respect to dredging or any other “works
                 of improvement”, any such duty in customary or treaty law does not
                 apply to the facts of the case. In any event, Nicaragua asserts that a duty
                 to notify and consult would not be triggered because both countries’
                 studies have shown that Nicaragua’s dredging programme posed no like-
                 lihood of significant transboundary harm. Nicaragua further argues that
                 neither Article 3, paragraph 2, nor Article 5 of the Ramsar Convention is
                 applicable to the facts of the case. With respect to the Convention for the
                 Conservation of the Biodiversity and Protection of Priority Wilderness
                 Areas in Central America, Nicaragua asserts that it does not set out an
                 obligation to share information relating to activities which may be par-
                 ticularly damaging to biological resources ; at most it encourages States to
                 do so.

                                                       *
                    108. The Court observes that the fact that the 1858 Treaty may con-
                 tain limited obligations concerning notification or consultation in specific
                 situations does not exclude any other procedural obligations with regard
                 to transboundary harm which may exist in treaty or customary interna-
                 tional law. In any event, the Court finds that, since Nicaragua was not
                 under an international obligation to carry out an environmental impact
                 assessment in light of the absence of risk of significant transboundary
                 harm (see paragraph 105 above), it was not required to notify, or consult
                 with, Costa Rica.

                    109. As to the alleged existence of an obligation to notify and consult
                 in treaties binding on the Parties, the Court observes that both Costa Rica

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                  and Nicaragua are parties to the Ramsar Convention and the Convention
                  for the Conservation of the Biodiversity and Protection of Priority
                 Wilderness Areas in Central America. The Court recalls that Article 3,
                  paragraph 2, of the Ramsar Convention provides that :

                        “Each Contracting Party shall arrange to be informed at the earli-
                     est possible time if the ecological character of any wetland in its ter-
                     ritory and included in the List [of wetlands of international importance]
                     has changed, is changing or is likely to change as the result of tech-
                     nological developments, pollution or other human interference. Infor-
                     mation on such changes shall be passed without delay to the [Ramsar
                     Secretariat].”

                 While this provision contains an obligation to notify, that obligation is
                 limited to notifying the Ramsar Secretariat of changes or likely changes
                 in the “ecological character of any wetland” in the territory of the notify-
                 ing State. In the present case, the evidence before the Court does not
                 indicate that Nicaragua’s dredging programme has brought about any
                 changes in the ecological character of the wetland, or that it was likely to
                 do so unless it were to be expanded. Thus the Court finds that no obliga-
                 tion to inform the Ramsar Secretariat arose for Nicaragua.

                   110. The Court further recalls that Article 5 of the Ramsar Convention
                 provides that :
                        “The Contracting Parties shall consult with each other about imple-
                     menting obligations arising from the Convention especially in the case
                     of a wetland extending over the territories of more than one Contract-
                     ing Party or where a water system is shared by Contracting Parties.
                     They shall at the same time endeavour to co‑ordinate and support
                     present and future policies and regulations concerning the conserva-
                     tion of wetlands and their flora and fauna.”

                 While this provision contains a general obligation to consult “about
                 implementing obligations arising from the Convention”, it does not cre-
                 ate an obligation on Nicaragua to consult with Costa Rica concerning a
                 particular project that it is undertaking, in this case the dredging of the
                 Lower San Juan River. In light of the above, Nicaragua was not required
                 under the Ramsar Convention to notify, or consult with, Costa Rica
                 prior to commencing its dredging project.
                   111. As to the Convention for the Conservation of the Biodiversity
                 and Protection of Priority Wilderness Areas in Central America, the
                 Court sees no need to take its enquiry further, as neither of the two provi-

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                 sions invoked by Costa Rica contains a binding obligation to notify or
                 consult.

                     (c) Conclusion
                    112. In light of the above, the Court concludes that it has not been
                 established that Nicaragua breached any procedural obligations owed to
                 Costa Rica under treaties or the customary international law of the envir
                 onment. The Court takes note of Nicaragua’s commitment, made in the
                 course of the oral proceedings, to carry out a new Environmental Impact
                 Study before any substantial expansion of its current dredging pro-
                 gramme. The Court further notes that Nicaragua stated that such a study
                 would include an assessment of the risk of transboundary harm, and that
                 it would notify, and consult with, Costa Rica as part of that process.

                 2. Substantive obligations concerning transboundary harm
                    113. The Court has already found that Nicaragua is responsible for the
                 harm caused by its activities in breach of Costa Rica’s territorial sover-
                 eignty. What remains to be examined is whether Nicaragua is responsible
                 for any transboundary harm allegedly caused by its dredging activities
                 which have taken place in areas under Nicaragua’s territorial sovereignty,
                 in the Lower San Juan River and on its left bank.

                    114. Costa Rica submits that Nicaragua has breached “the obligation
                 not to dredge, divert or alter the course of the San Juan River, or conduct
                 any other works on the San Juan River, if this causes damage to
                 Costa Rican territory (including the Colorado River), its environment, or
                 to Costa Rican rights under the 1888 Cleveland Award” (final submis-
                 sions, para. 2 (c) (v)). According to Costa Rica, the dredging programme
                 executed by Nicaragua in the Lower San Juan River was in breach of
                 Nicaragua’s obligations under customary international law and caused
                 harm to Costa Rican lands on the right bank of the river and to the
                 Colorado River.

                   115. Nicaragua contends that the dredging programme has not caused
                 any harm to Costa Rican territory including the Colorado River. It
                 argues that the execution of the dredging programme has been beneficial
                 to the dredged section of the Lower San Juan River and to the wetlands
                 of international importance lying downstream. Moreover, Nicaragua
                 maintains that, under a special rule stated in the Cleveland Award and
                 applying to the San Juan River, even if damage to Costa Rica’s territory
                 resulted from the works to maintain and improve the river, the dredging
                 activities would not be unlawful.

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                   116. Both Parties referred to the passage in the Cleveland Award which
                 reads as follows :
                         “The Republic of Costa Rica cannot prevent the Republic of Nic-
                      aragua from executing at her own expense and within her own terri-
                      tory such works of improvement, provided such works of improvement
                      do not result in the occupation or flooding or damage of Costa Rica
                      territory, or in the destruction or serious impairment of the navigation
                      of the said river or any of its branches at any point where Costa Rica
                      is entitled to navigate the same. The Republic of Costa Rica has the
                      right to demand indemnification for any places belonging to her on
                      the right bank of the River San Juan which may be occupied without
                      her consent, and for any lands on the same bank which may be
                      flooded or damaged in any other way in consequence of works of
                      improvement.” (RIAA, Vol. XXVIII, p. 210, para. 3 (6) ; emphasis in
                      the original.)

                 Both Parties also referred to the following passage in the same Award :

                        “The Republic of Costa Rica can deny to the Republic of Nicara-
                      gua the right of deviating the waters of the River San Juan in case
                      such deviation will result in the destruction or serious impairment of
                      the navigation of the said river or any of its branches at any point
                      where Costa Rica is entitled to navigate the same.” (Ibid., para. 3 (9).)

                    117. According to Nicaragua, the statements in the Cleveland Award
                 quoted above should be understood as implying that Nicaragua is free to
                 undertake any dredging activity, possibly even if it is harmful to
                 Costa Rica. On the other hand, according to Costa Rica, Nicaragua
                 would be under an obligation to pay compensation for any harm caused
                 to Costa Rica, whether the harm was significant or not and whether Nica-
                 ragua was or was not diligent in ensuring that the environment of
                 Costa Rica would not be affected ; damage caused by “unforeseeable or
                 uncontrollable events” related to dredging activities would also have to
                 be compensated by Nicaragua. Costa Rica also argued that “all of Nica-
                 ragua’s rights and obligations under the 1858 Treaty and the 1888 Award
                 must be interpreted in the light of principles for the protection of the
                 environment in force today” and that the Treaty and the Award do not
                 “override the application of environmental obligations under general
                 principles of law and under international treaties” requiring States not to
                 cause significant transboundary harm.
                    118. As the Court restated in the Pulp Mills case, under customary
                 international law, “[a] State is . . . obliged to use all the means at its dis-
                 posal in order to avoid activities which take place in its territory, or in
                 any area under its jurisdiction, causing significant damage to the environ-
                 ment of another State” (I.C.J. Reports 2010 (I), p. 56, para. 101 ; see also

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                       certain activities and construction of a road (judgment)        712

                 Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion,
                 I.C.J. Reports 1996 (I), pp. 241‑242, para. 29).

                    In any event, it would be necessary for the Court to address the ques-
                 tion of the relationship between the 1858 Treaty as interpreted by the
                 Cleveland Award and the current rule of customary international law
                 with regard to transboundary harm only if Costa Rica were to prove that
                 the dredging programme in the Lower San Juan River produced harm to
                 Costa Rica’s territory.
                    119. Costa Rica has not provided any convincing evidence that sedi-
                 ments dredged from the river were deposited on its right bank. Costa Rica
                 has also not proved that the dredging programme caused harm to its wet-
                 land (see paragraph 109 above). With regard to Costa Rica’s contention
                 that “the dredging programme has had a significant effect upon the Colo-
                 rado River”, it has already been noted that the Parties agree that at the
                 so‑called “Delta Colorado” the Colorado River receives about 90 per cent
                 of the waters flowing through the San Juan River (see paragraph 56
                 above). Nicaragua estimates that the diversion of water from the Colo-
                 rado River due to the dredging of the Lower San Juan River affected less
                 than 2 per cent of the waters flowing into the Colorado River. No higher
                 figure has been suggested by Costa Rica. Its main expert observed that
                 “there is no evidence that the dredging programme has significantly
                 affected flows in the Río Colorado”. Costa Rica did adduce evidence indi-
                 cating a significant reduction in flow of the Colorado River between Jan-
                 uary 2011 and October 2014. However, the Court considers that a causal
                 link between this reduction and Nicaragua’s dredging programme has not
                 been established. As Costa Rica admits, other factors may be relevant to
                 the decrease in flow, most notably the relatively small amount of rainfall
                 in the relevant period. In any event, the diversion of water due to the
                 dredging of the Lower San Juan River is far from seriously impairing
                 navigation on the Colorado River, as envisaged in paragraph 3 (9) of the
                 Cleveland Award, or otherwise causing harm to Costa Rica.

                   120. The Court therefore concludes that the available evidence does
                 not show that Nicaragua breached its obligations by engaging in dredging
                 activities in the Lower San Juan River.

                                 C. Compliance with Provisional Measures
                    121. In its final submissions Costa Rica contends that Nicaragua has
                 also breached its “obligations arising from the Orders of the Court indi-
                 cating provisional measures of 8 March 2011 and 22 November 2013”
                 (para. 2 (c) (vi)).
                    122. Nicaragua, for its part, raised certain issues about Costa Rica’s
                 compliance with some of the provisional measures adopted by the Court,
                 but did not request the Court to make a finding on this matter.

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                      certain activities and construction of a road (judgment)             713

                    123. In its Order on provisional measures of 8 March 2011 the Court
                 indicated that “[e]ach Party shall refrain from sending to, or maintaining in
                 the disputed territory, including the caño, any personnel, whether civilian,
                 police or security” ; the Court also required each Party to “refrain from any
                 action which might aggravate or extend the dispute before the Court or
                 make it more difficult to resolve” (I.C.J. Reports 2011 (I), p. 27, para. 86).
                    124. Costa Rica argued that the presence in the disputed territory of
                 large groups of Nicaraguan civilians who were members of an environ-
                 mental movement constituted a breach of the 2011 Order. Nicaragua
                 denied this. In its Order of 16 July 2013, the Court specified that “the
                 presence of organized groups of Nicaraguan nationals in the disputed
                 area carrie[d] the risk of incidents which might aggravate the . . . dispute”
                 (I.C.J. Reports 2013, p. 240, para. 37).

                    125. Costa Rica maintained and Nicaragua later acknowledged that
                 the excavation of the second and third caños took place after the 2011
                 Order had been adopted, that this activity was attributable to Nicaragua
                 and that moreover a military encampment had been installed on the dis-
                 puted territory as defined by the Court. In the oral hearings Nicaragua
                 also acknowledged that the excavation of the second and third caños rep-
                 resented an infringement of its obligations under the 2011 Order.

                    126. The Court already ascertained these facts in its Order of
                 22 November 2013 (ibid., pp. 364‑365, paras. 45‑46). However, that state-
                 ment was only instrumental in ensuring the protection of the rights of the
                 Parties during the judicial proceedings. The judgment on the merits is the
                 appropriate place for the Court to assess compliance with the provisional
                 measures. Thus, contrary to what was argued by Nicaragua, a statement
                 of the existence of a breach to be included in the present Judgment cannot
                 be viewed as “redundant”. Nor can it be said that any responsibility for
                 the breach has ceased : what may have ceased is the breach, not the
                 responsibility arising from the breach.
                    127. On the basis of the facts that have become uncontested, the Court
                 accordingly finds that Nicaragua breached its obligations under the Order
                 of 8 March 2011 by excavating two caños and establishing a military pres-
                 ence in the disputed territory.
                    128. The Court’s Order of 22 November 2013 required the following
                 measures from Nicaragua : to “refrain from any dredging and other activ-
                 ities in the disputed territory” ; to “fill the trench on the beach north of
                 the eastern caño” ; to “cause the removal from the disputed territory of
                 any personnel, whether civilian, police or security” ; to “prevent any such
                 personnel from entering the disputed territory” ; and to “cause the
                 removal from and prevent the entrance into the disputed territory of any
                 private persons under its jurisdiction or control” (ibid., p. 369, para. 59).
                 No allegations of subsequent breaches of any of these obligations were
                 made by Costa Rica, which only maintained that some of Nicaragua’s
                 activities after this Order were in breach of its obligation not to aggravate

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                      certain activities and construction of a road (judgment)          714

                 the dispute, which had been stated in the 2011 Order. The Court does not
                 find that a breach of this obligation has been demonstrated on the basis
                 of the available evidence.
                    129. The Court thus concludes that Nicaragua acted in breach of its
                 obligations under the 2011 Order by excavating the second and third
                 caños and by establishing a military presence in the disputed territory.
                 The Court observes that this finding is independent of the conclusion set
                 out above (see Section A) that the same conduct also constitutes a viola-
                 tion of the territorial sovereignty of Costa Rica.

                                          D. Rights of Navigation
                    130. In its final submissions Costa Rica also claims that Nicaragua has
                 breached “Costa Rica’s perpetual rights of free navigation on the San
                 Juan in accordance with the 1858 Treaty of Limits, the 1888 Cleveland
                 Award and the Court’s Judgment of 13 July 2009” (final submissions,
                 para. 2 (c) (ii)).
                    131. Nicaragua contests the admissibility of this submission, which it
                 considers not covered by the Application and as having an object uncon-
                 nected with that of the “main dispute”. Costa Rica points out that it had
                 already requested in its Application (para. 41 (f)) that the Court adjudge
                 and declare that, “by its conduct, Nicaragua has breached . . . the obliga-
                 tion not to prohibit the navigation on the San Juan River by Costa Rican
                 nationals”.
                    132. The Court observes that, although Costa Rica’s submission could
                 have been understood as related to the “dredging and canalization activi-
                 ties being carried out by Nicaragua on the San Juan River”, to which the
                 same paragraph of the Application also referred, the wording of the sub-
                 mission quoted above did not contain any restriction to that effect. The
                 Court considers that Costa Rica’s final submission concerning rights of
                 navigation is admissible.
                    133. Article VI of the 1858 Treaty provides that :
                         “The Republic of Nicaragua shall have exclusive dominium and
                      imperium over the waters of the San Juan River from its origin in the
                      lake to its mouth at the Atlantic Ocean ; the Republic of Costa Rica
                      shall however have a perpetual right of free navigation on the said
                      waters between the mouth of the river and a point located three Eng-
                      lish miles below Castillo Viejo, [con objetos de comercio], whether
                      with Nicaragua or with the interior of Costa Rica by the rivers San
                      Carlos or Sarapiquí or any other waterway starting from the section
                      of the bank of the San Juan established as belonging to that Repub-
                      lic. The vessels of both countries may land indiscriminately on either
                      bank of the section of the river where navigation is common, without
                      paying any taxes, unless agreed by both Governments.” (Translation
                      from the Spanish original as reproduced in Dispute regarding Naviga‑

                                                                                53

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                      certain activities and construction of a road (judgment)              715

                      tional and Related Rights (Costa Rica v. Nicaragua), Judgment,
                      I.C.J. Reports 2009, p. 236, para. 44: “La República de Nicaragua
                      tendrá exclusivamente el dominio y sumo imperio sobre las aguas del
                      río de San Juan desde su salida del Lago, hasta su desembocadura en
                      el Atlántico ; pero la República de Costa Rica tendrá en dichas aguas
                      los derechos perpetuos de libre navegación, desde la expresada desem‑
                      bocadura hasta tres millas inglesas antes de llegar al Castillo Viejo, con
                      objetos de comercio, ya sea con Nicaragua ó al interior de Costa Rica,
                      por los ríos de San Carlos ó Sarapiquí, ó cualquiera otra vía procedente
                      de la parte que en la ribera del San Juan se establece corresponder á
                      esta República. Las embarcaciones de uno ú otro país podrán indistin‑
                      tamente atracar en las riberas del río en la parte en que la navegación
                      es común, sin cobrarse ninguna clase de impuestos, á no ser que se
                      establezcan de acuerdo entre ambos Gobiernos.”)

                 The Cleveland Award contains some references to Costa Rica’s rights of
                 navigation that were quoted above (see paragraph 116). In its Judgment
                 in Dispute regarding Navigational and Related Rights (Costa Rica v. Nica‑
                 ragua), the Court noted that :
                      “two types of private navigation are certainly covered by the right of
                      free navigation pursuant to Article VI of the 1858 Treaty : the navi-
                      gation of vessels carrying goods intended for commercial transac-
                      tions ; and that of vessels carrying passengers who pay a price other
                      than a token price (or for whom a price is paid) in exchange for the
                      service thus provided” (I.C.J. Reports 2009, p. 245, para. 73).

                 While the express language of Article VI of the 1858 Treaty only consid-
                 ered navigation for purposes of commerce, the Court also observed that :
                      “it cannot have been the intention of the authors of the 1858 Treaty
                      to deprive the inhabitants of the Costa Rican bank of the river, where
                      that bank constitutes the boundary between the two States, of the
                      right to use the river to the extent necessary to meet their essential
                      requirements, even for activities of a non‑commercial nature, given
                      the geography of the area” (ibid., p. 246, para. 79).
                 In the operative part of the same Judgment, the Court found that :
                      “the inhabitants of the Costa Rican bank of the San Juan River have
                      the right to navigate on the river between the riparian communities
                      for the purposes of the essential needs of everyday life which require
                      expeditious transportation” (ibid., p. 270, para. 156 (1) (f)).
                   134. Costa Rica includes among the alleged breaches of its rights of
                 navigation the enactment by Nicaragua of Decree No. 079‑2009 of
                 1 October 2009, concerning navigation on the San Juan River. The inter-
                 pretation of this decree is controversial between the Parties : Costa Rica

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                      certain activities and construction of a road (judgment)           716

                 considers that the decree is of general application, whereas Nicaragua
                 contends that it applies only to tourist boats. While it is clear that the
                 decree should be consistent with Article VI of the 1858 Treaty as inter-
                 preted by the Court, the Court observes that none of the instances of
                 interference with Costa Rica’s rights of navigation specifically alleged by
                 Costa Rica relates to the application of Decree No. 079‑2009. The Court
                 is therefore not called upon to examine this decree.
                    135. Costa Rica alleges that breaches of its rights of navigation
                 occurred in five instances. Nicaragua emphasizes the small number of
                 alleged breaches, but does not contest two of those incidents. In the first
                 one, in February 2013, a riparian farmer and his uncle were detained for
                 several hours at a Nicaraguan army post and subjected to humiliating
                 treatment. This incident is set out in an affidavit. In the second incident,
                 in June 2014, a Costa Rican property owner and some members of a local
                 agricultural co-operative were prevented by Nicaraguan agents from nav-
                 igating the San Juan River. This is supported by five affidavits.

                    136. The Court finds that Nicaragua did not provide a convincing jus-
                 tification with regard to Article VI of the 1858 Treaty for the conduct of
                 its authorities in these two incidents concerning navigation by inhabitants
                 of the Costa Rican bank of the San Juan River. The Court concludes that
                 the two incidents show that Nicaragua breached Costa Rica’s rights of
                 navigation on the San Juan River pursuant to the 1858 Treaty. Given this
                 finding, it is unnecessary for the Court to examine the other incidents
                 invoked by Costa Rica.

                                               E. Reparation
                   137. Costa Rica requests the Court to order Nicaragua to “repeal, by
                 means of its own choosing, those provisions of the Decree No. 079‑2009
                 and the Regulatory Norms annexed thereto of 1 October 2009 which are
                 contrary to Costa Rica’s right of free navigation under Article VI of the
                 1858 Treaty of Limits, the 1888 Cleveland Award, and the Court’s Judg-
                 ment of 13 July 2009” and to cease all dredging activities in the San Juan
                 River pending the fulfilment of certain conditions (final submissions,
                 para. 3 (a) and (b)).
                   Costa Rica moreover asks the Court to order Nicaragua to :

                      “make reparation in the form of compensation for the material dam-
                      age caused to Costa Rica, including but not limited to: (i) damage
                      arising from the construction of artificial caños and destruction of
                      trees and vegetation on the ‘disputed territory’; (ii) the cost of the
                      remediation measures carried out by Costa Rica in relation to those
                      damages . . . ; the amount of such compensation to be determined in
                      a separate phase of these proceedings” (ibid., para. 3 (c)).

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                 The Court is further requested to order Nicaragua to “provide satisfac-
                 tion so [as] to achieve full reparation of the injuries caused to Costa Rica
                 in a manner to be determined by the Court” (final submissions,
                 para. 3 (d)) and to “provide appropriate assurances and guarantees of
                 non‑repetition of Nicaragua’s unlawful conduct, in such a form as the
                 Court may order” (ibid., para. 3 (e)). Costa Rica finally requests an
                 award of costs that will be considered later in the present section.

                    138. In view of the conclusions reached by the Court in Sections B and D
                 above, the requests made by Costa Rica in its final submissions under
                 paragraph 3 (a) and (b), concerning the repeal of the Decree No. 079‑2009
                 on navigation and the cessation of dredging activities respectively, cannot
                 be granted.
                    139. The declaration by the Court that Nicaragua breached the territo-
                 rial sovereignty of Costa Rica by excavating three caños and establishing
                 a military presence in the disputed territory provides adequate satisfac-
                 tion for the non‑material injury suffered on this account. The same applies
                 to the declaration of the breach of the obligations under the Court’s
                 Order of 8 March 2011 on provisional measures. Finally, the declaration
                 of the breach of Costa Rica’s rights of navigation in the terms determined
                 above in Section D provides adequate satisfaction for that breach.

                    140. The request for “appropriate assurances and guarantees of
                 non‑repetition” was originally based on Nicaragua’s alleged “bad faith”
                 in the dredging of the 2010 caño and later on Nicaragua’s infringement of
                 its obligations under the 2011 Order.

                    141. As the Court noted in the Navigational and Related Rights case,
                 “there is no reason to suppose that a State whose act or conduct has been
                 declared wrongful by the Court will repeat that act or conduct in the
                 future, since its good faith must be presumed” and therefore assurances
                 and guarantees of non‑repetition will be ordered only “in special circum-
                 stances” (I.C.J. Reports 2009, p. 267, para. 150). While Nicaragua failed
                 to comply with the obligations under the 2011 Order, it is necessary also
                 to take into account the fact that Nicaragua later complied with the
                 requirements, stated in the Order of 22 November 2013, to “refrain from
                 any dredging and other activities in the disputed territory” and to “cause
                 the removal from the disputed territory of any personnel, whether civil-
                 ian, police or security” (I.C.J. Reports 2013, p. 369, para. 59). It is to be
                 expected that Nicaragua will have the same attitude with regard to the
                 legal situation resulting from the present Judgment, in particular in view
                 of the fact that the question of territorial sovereignty over the disputed
                 territory has now been resolved.

                   142. Costa Rica is entitled to receive compensation for the material
                 damage caused by those breaches of obligations by Nicaragua that have

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                 been ascertained by the Court. The relevant material damage and the
                 amount of compensation may be assessed by the Court only in separate
                 proceedings. The Court is of the opinion that the Parties should engage in
                 negotiation in order to reach an agreement on these issues. However, if
                 they fail to reach such an agreement within 12 months of the date of the
                 present Judgment, the Court will, at the request of either Party, determine
                 the amount of compensation on the basis of further written pleadings
                 limited to this issue.

                                                       *
                      143. Costa Rica also requests the Court to order Nicaragua to :

                        “pay all of the costs and expenses incurred by Costa Rica in request-
                        ing and obtaining the Order on provisional measures of 22 November
                        2013, including, but not limited to, the fees and expenses of
                        Costa Rica’s counsel and experts, with interest, on a full indemnity
                        basis” (final submissions, para. 3 (f)).

                 The special reason for this request is that the proceedings which led to the
                 Order of 22 November 2013 were allegedly due to the infringements by
                 Nicaragua of its obligations under the Order of 8 March 2011.

                    144. According to Article 64 of the Statute, “[u]nless otherwise decided
                 by the Court, each party shall bear its own costs”. This Article provides
                 that as a rule, costs are not awarded to any of the parties, but gives the
                 Court the power to order that one of them will pay some or all of the
                 costs. While the breach by Nicaragua of its obligations under the
                 2011 Order necessitated Costa Rica engaging in new proceedings on pro-
                 visional measures, the Court finds that, taking into account the overall
                 circumstances of the case, an award of costs to Costa Rica, as the latter
                 requested, would not be appropriate.

                               IV. Issues in the Nicaragua v. Costa Rica Case

                    145. The Application filed by Nicaragua on 22 December 2011 (see
                 paragraph 9 above) concerns the alleged breach by Costa Rica of both
                 procedural and substantive obligations in connection with the construc-
                 tion of the road along the San Juan River. The Court will start by consid-
                 ering the alleged breach of procedural obligations ; then it will address the
                 alleged breach of substantive obligations.

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                              A. The Alleged Breach of Procedural Obligations
                 1. The alleged breach of the obligation to carry out an environmental
                    impact assessment
                     146. According to Nicaragua, Costa Rica breached its obligation
                 under general international law to assess the environmental impact of the
                 construction of the road before commencing it, particularly in view of the
                 road’s length and location.
                     147. Costa Rica denies the allegation. It argues that the construction
                 of the road did not create a risk of significant transboundary harm
                 through the discharge of harmful substances into the San Juan River or
                 otherwise into Nicaraguan territory, and that there was no risk that the
                 river would be materially affected by the relatively insignificant quantities
                 of sediment coming from the road.
                     148. Costa Rica also maintains that it was exempted from the require-
                 ment to prepare an environmental impact assessment because of the state
                 of emergency created by Nicaragua’s occupation of Isla Portillos (see
                 paragraphs 63‑64 above). First, Costa Rica argues that an emergency can
                 exempt a State from the requirement to conduct an environmental impact
                 assessment, either because international law contains a renvoi to domestic
                 law on this point, or because it includes an exemption for emergency situ-
                 ations. Secondly, Costa Rica submits that the construction of the road
                 was an appropriate response to the emergency situation because it would
                 facilitate access to the police posts and remote communities located along
                 the right bank of the San Juan River, particularly in light of the real risk
                 of a military confrontation with Nicaragua, which would require
                 Costa Rica to evacuate the area. Thus, Costa Rica claims that it could
                 proceed with its construction works without an environmental impact
                 assessment.
                     149. In any event, Costa Rica maintains that, even if it was required
                 under international law to conduct an environmental impact assessment
                 in this case, it fulfilled the obligation by carrying out a number of envir
                 onmental impact studies, including an “Environmental Diagnostic
                 Assessment” in 2013.
                     150. In reply, Nicaragua argues that there was no bona fide emergency.
                  It states that the road is not located near the disputed territory, as defined
                  by the Court’s Order of 8 March 2011, and that the emergency was
                  declared several months after the beginning of the construction works.
                  Nicaragua further argues that there is no emergency exemption from the
                  international obligation to carry out an environmental impact assess-
                  ment. It points out that Costa Rica improperly seeks to rely on a declara-
                 tion of emergency made under its domestic law to justify its failure to
                 perform its international law obligations.

                    151. Finally, Nicaragua points out that the environmental impact
                 studies produced by Costa Rica after the bulk of the construction work

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                 had been completed do not constitute an adequate environmental impact
                 assessment. As a consequence, it asks the Court to declare that Costa Rica
                 should not undertake any future development in the area without an
                 appropriate environmental impact assessment.
                    152. Following the lines of argument put forward by the Parties, the
                 Court will first examine whether Costa Rica was under an obligation to
                 carry out an environmental impact assessment under general interna-
                 tional law. If so, the Court will assess whether it was exempted from the
                 said obligation or whether it complied with that obligation by carrying
                 out the Environmental Diagnostic Assessment and other studies.

                                                      *
                    153. The Court recalls (see paragraph 104 above) that a State’s obliga-
                 tion to exercise due diligence in preventing significant transboundary
                 harm requires that State to ascertain whether there is a risk of significant
                 transboundary harm prior to undertaking an activity having the potential
                 adversely to affect the environment of another State. If that is the case,
                 the State concerned must conduct an environmental impact assessment.
                 The obligation in question rests on the State pursuing the activity.
                 Accordingly, in the present case, it fell on Costa Rica, not on Nicaragua,
                 to assess the existence of a risk of significant transboundary harm prior to
                 the construction of the road, on the basis of an objective evaluation of all
                 the relevant circumstances.

                    154. In the oral proceedings, counsel for Costa Rica stated that a pre-
                 liminary assessment of the risk posed by the road project was undertaken
                 when the decision to build the road was made. According to Costa Rica,
                 this assessment took into account the nature of the project and its likely
                 impact on the river, and concluded that the road posed no risk of signifi-
                 cant harm. In support of this claim, Costa Rica emphasized the modest
                 scale of the works, that the road was clearly not a highway, that some of
                 it was constructed on pre‑existing tracks, and that the only possible risk
                 was the contribution of sediment by the road to a river that already car-
                 ried a heavy sediment load.
                    The Court observes that to conduct a preliminary assessment of the
                 risk posed by an activity is one of the ways in which a State can ascertain
                 whether the proposed activity carries a risk of significant transboundary
                 harm. However, Costa Rica has not adduced any evidence that it actually
                 carried out such a preliminary assessment.
                    155. In evaluating whether, as of the end of 2010, the construction of
                 the road posed a risk of significant transboundary harm, the Court will
                 have regard to the nature and magnitude of the project and the context in
                 which it was to be carried out.
                    First, the Court notes that, contrary to Costa Rica’s submission,
                 the scale of the road project was substantial. The road, which is
                 nearly 160 km long, runs along the river for 108.2 km (see sketch‑map

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                 No. 2 above). Approximately half of that stretch is completely new con-
                 struction.
                    Secondly, the Court notes that, because of the planned location of the
                 road along the San Juan River, any harm caused by the road to the sur-
                 rounding environment could easily affect the river, and therefore Nicara-
                 gua’s territory. The evidence before the Court shows that approximately
                 half of the stretch of road following the San Juan River is situated within
                 100 metres of the river bank ; for nearly 18 km it is located within
                 50 metres of the river ; and in some stretches it comes within 5 metres of
                 the right bank of the river. The location of the road in such close proxim-
                 ity to the river and the fact that it would often be built on slopes, risked
                 increasing the discharge of sediment into the river. Another relevant fac-
                 tor in assessing the likelihood of sedimentation due to erosion from the
                 road is that almost a quarter of the road was to be built in areas that were
                 previously forested. The possibility of natural disasters in the area caused
                 by adverse events such as hurricanes, tropical storms and earthquakes,
                 which would increase the risk of sediment erosion, must equally be taken
                 into consideration.
                    Thirdly, the geographic conditions of the river basin where the road
                 was to be situated must be taken into account. The road would pass
                 through a wetland of international importance in Costa Rican territory
                 and be located in close proximity to another protected wetland — the
                 Refugio de Vida Silvestre Río San Juan — situated in Nicaraguan terri-
                 tory. The presence of Ramsar protected sites heightens the risk of signifi-
                 cant damage because it denotes that the receiving environment is
                 particularly sensitive. The principal harm that could arise was the possi-
                 ble large deposition of sediment from the road, with resulting risks to the
                 ecology and water quality of the river, as well as morphological changes.

                   156. In conclusion, the Court finds that the construction of the road by
                 Costa Rica carried a risk of significant transboundary harm. Therefore,
                 the threshold for triggering the obligation to evaluate the environmental
                 impact of the road project was met.

                                                      *
                    157. The Court now turns to the question of whether Costa Rica was
                 exempted from its obligation to evaluate the environmental impact of the
                 road project because of an emergency. First, the Court recalls its holding
                 that “it is for each State to determine in its domestic legislation or in the
                 authorization process for the project, the specific content of the environ-
                 mental impact assessment required in each case”, having regard to vari-
                 ous factors (see paragraph 104 above, quoting Pulp Mills on the River
                 Uruguay (Argentina v. Uruguay), Judgment, I.C.J. Reports 2010 (I),
                 p. 83, para. 205). The Court observes that this reference to domestic law
                 does not relate to the question of whether an environmental impact
                 assessment should be undertaken. Thus, the fact that there may be an

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                 emergency exemption under Costa Rican law does not affect Costa Rica’s
                 obligation under international law to carry out an environmental impact
                 assessment.

                    158. Secondly, independently of the question whether or not an emer-
                 gency could exempt a State from its obligation under international law to
                 carry out an environmental impact assessment, or defer the execution of
                 this obligation until the emergency has ceased, the Court considers that,
                 in the circumstances of this case, Costa Rica has not shown the existence
                 of an emergency that justified constructing the road without undertaking
                 an environmental impact assessment. In fact, completion of the project
                 was going to take, and is indeed taking, several years. In addition, when
                 Costa Rica embarked upon the construction of the road, the situation in
                 the disputed territory was before the Court, which shortly thereafter
                 issued provisional measures. Although Costa Rica maintains that the
                 construction of the road was meant to facilitate the evacuation of the area
                 of Costa Rican territory adjoining the San Juan River, the Court notes
                 that the road provides access to only part of that area and thus could
                 constitute a response to the alleged emergency only to a limited extent.
                 Moreover, Costa Rica has not shown an imminent threat of military con-
                 frontation in the regions crossed by the road. Finally, the Court notes
                 that the Executive Decree proclaiming an emergency was issued by
                 Costa Rica on 21 February 2011, after the works on the road had begun.

                    159. Having thus concluded that, in the circumstances of this case,
                 there was no emergency justifying the immediate construction of the road,
                 the Court does not need to decide whether there is an emergency exemp-
                 tion from the obligation to carry out an environmental impact assessment
                 in cases where there is a risk of significant transboundary harm.
                    It follows that Costa Rica was under an obligation to conduct an envir
                 onmental impact assessment prior to commencement of the construction
                 works.

                                                     *
                    160. Turning now to the question of whether Costa Rica complied
                 with its obligation to carry out an environmental impact assessment, the
                 Court notes that Costa Rica produced several studies, including an Envir
                 onmental Management Plan for the road in April 2012, an Environmen-
                 tal Diagnostic Assessment in November 2013, and a follow‑up study
                 thereto in January 2015. These studies assessed the adverse effects that
                 had already been caused by the construction of the road on the environ-
                 ment and suggested steps to prevent or reduce them.

                   161. In its Judgment in the Pulp Mills case, the Court held that the
                 obligation to carry out an environmental impact assessment is a continu-
                 ous one, and that monitoring of the project’s effects on the environment

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                 shall be undertaken, where necessary, throughout the life of the project
                 (I.C.J. Reports 2010 (I), pp. 83‑84, para. 205). Nevertheless, the obliga-
                 tion to conduct an environmental impact assessment requires an ex ante
                 evaluation of the risk of significant transboundary harm, and thus “an
                 environmental impact assessment must be conducted prior to the imple-
                 mentation of a project” (ibid., p. 83, para. 205). In the present case,
                 Costa Rica was under an obligation to carry out such an assessment prior
                 to commencing the construction of the road, to ensure that the design
                 and execution of the project would minimize the risk of significant trans-
                 boundary harm. In contrast, Costa Rica’s Environmental Diagnostic
                 Assessment and its other studies were post hoc assessments of the environ-
                 mental impact of the stretches of the road that had already been built.
                 These studies did not evaluate the risk of future harm. The Court notes
                 moreover that the Environmental Diagnostic Assessment was carried out
                 approximately three years into the road’s construction.
                    162. For the foregoing reasons, the Court concludes that Costa Rica
                 has not complied with its obligation under general international law to
                 carry out an environmental impact assessment concerning the construc-
                 tion of the road.

                 2. The alleged breach of Article 14 of the Convention on Biological Diversity

                    163. Nicaragua submits that Costa Rica was required to carry out an
                 environmental impact assessment by Article 14 of the Convention on Bio-
                 logical Diversity. Costa Rica responds that the provision at issue con-
                 cerns the introduction of appropriate procedures with respect to projects
                 that are likely to have a significant adverse effect on biological diversity.
                 It claims that it had such procedures in place and that, in any event, they
                 do not apply to the construction of the road, as it was not likely to have
                 a significant adverse effect on biological diversity.

                      164. The Court recalls that the provision reads, in relevant part :

                           “Each Contracting Party, as far as possible and as appropriate,
                        shall: (a) Introduce appropriate procedures requiring environmental
                        impact assessment of its proposed projects that are likely to have
                        significant adverse effects on biological diversity with a view to avoid-
                        ing or minimizing such effects and, where appropriate, allow for pub-
                        lic participation in such procedures.”
                 The Court considers that the provision at issue does not create an obliga-
                 tion to carry out an environmental impact assessment before undertaking
                 an activity that may have significant adverse effects on biological diver-
                 sity. Therefore, it has not been established that Costa Rica breached Arti-
                 cle 14 of the Convention on Biological Diversity by failing to conduct an
                 environmental impact assessment for its road project.

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                 3. The alleged breach of an obligation to notify and consult
                   165. Nicaragua contends that Costa Rica breached its obligation to
                 notify, and consult with, Nicaragua in relation to the construction works.
                 Nicaragua founds the existence of such obligation on three grounds, namely,
                 customary international law, the 1858 Treaty, and the Ramsar Con
                 vention. The Court will examine each of Nicaragua’s arguments in turn.

                                                       *
                    166. In Nicaragua’s view, Costa Rica should have notified it of the
                 road project and should have consulted with it, as Costa Rica had every
                 reason to believe that the construction of the road risked causing signifi-
                 cant transboundary harm. According to Nicaragua, the alleged emer-
                 gency did not exempt Costa Rica from this obligation.
                    167. For Costa Rica, the relevant threshold of “risk of significant
                 adverse impact” was not met in this case. Moreover, Costa Rica claims to
                 have invited Nicaragua to engage in consultations, but Nicaragua did not
                 do so. In any event, according to Costa Rica, Nicaragua is prevented
                 from relying on the obligation to notify since it has itself created the
                 emergency to which Costa Rica had to respond by constructing the road.

                    168. The Court reiterates its conclusion that, if the environmental
                 impact assessment confirms that there is a risk of significant transbound-
                 ary harm, a State planning an activity that carries such a risk is required,
                 in order to fulfil its obligation to exercise due diligence in preventing sig-
                 nificant transboundary harm, to notify, and consult with, the potentially
                 affected State in good faith, where that is necessary to determine the
                 appropriate measures to prevent or mitigate that risk (see paragraph 104
                 above). However, the duty to notify and consult does not call for exam
                 ination by the Court in the present case, since the Court has established
                 that Costa Rica has not complied with its obligation under general inter-
                 national law to perform an environmental impact assessment prior to the
                 construction of the road.

                                                       *
                    169. Nicaragua further asserts the existence of an obligation to notify
                 under the 1858 Treaty. In its 2009 Judgment in the Navigational Rights
                 case, the Court held that Nicaragua has an obligation to notify Costa Rica
                 of its regulations concerning navigation on the river. According to Nica-
                 ragua, since the construction of the road affects Nicaragua’s navigational
                 rights, the same reasoning applies a fortiori in this case.

                   170. For Costa Rica, Nicaragua’s reference to the 1858 Treaty is mis-
                 placed, since the Treaty does not impose on Costa Rica an obligation to

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                 notify Nicaragua if Costa Rica undertakes infrastructure works on its
                 own territory.
                   171. The Court recalls its finding in the 2009 Judgment that Nicara-
                 gua’s obligation to notify Costa Rica under the 1858 Treaty arises,
                 amongst other factors, by virtue of Costa Rica’s rights of navigation
                 on the river, which is part of Nicaragua’s territory (Dispute regarding
                 Navigational and Related Rights (Costa Rica v. Nicaragua), Judgment,
                 I.C.J. Reports 2009, pp. 251‑252, paras. 94‑97). In contrast, the
                 1858 Treaty does not grant Nicaragua any rights on Costa Rica’s terri-
                 tory, where the road is located. Therefore, no obligation to notify Nicara-
                 gua with respect to measures undertaken on Costa Rica’s territory arises.
                 The Court concludes that the 1858 Treaty did not impose on Costa Rica
                 an obligation to notify Nicaragua of the construction of the road.

                                                     *
                    172. Lastly, Nicaragua relies on Article 3, paragraph 2, and on Arti-
                 cle 5 of the Ramsar Convention (see paragraphs 109‑110 above) as impos-
                 ing an obligation of notification and consultation upon the Contracting
                 Parties. In the Court’s view, Nicaragua has not shown that, by construct-
                 ing the road, Costa Rica has changed or was likely to change the eco-
                 logical character of the wetland situated in its territory. Moreover,
                 contrary to Nicaragua’s contention, on 28 February 2012 Costa Rica
                 notified the Ramsar Secretariat about the stretch of the road that passes
                 through the Humedal Caribe Noreste. Therefore, the Court concludes that
                 Nicaragua has not shown that Costa Rica breached Article 3, para-
                 graph 2, of the Ramsar Convention. As regards Article 5 of the Ramsar
                 Convention, the Court finds that this provision creates no obligation for
                 Costa Rica to consult with Nicaragua concerning a particular project it is
                 undertaking, in this case the construction of the road (see also para-
                 graph 110 above).

                                                     *
                    173. In conclusion, the Court finds that Costa Rica failed to comply
                 with its obligation to evaluate the environmental impact of the construc-
                 tion of the road. Costa Rica remains under an obligation to prepare an
                 appropriate environmental impact assessment for any further works on
                 the road or in the area adjoining the San Juan River, should they carry a
                 risk of significant transboundary harm. Costa Rica accepts that it is under
                 such an obligation. There is no reason to suppose that it will not take
                 note of the reasoning and conclusions in this Judgment as it conducts any
                 future development in the area, including further construction works on
                 the road. The Court also notes Nicaragua’s commitment, made in the
                 course of the oral proceedings, that it will co‑operate with Costa Rica in

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                 assessing the impact of such works on the river. In this connection, the
                 Court considers that, if the circumstances so require, Costa Rica will have
                 to consult in good faith with Nicaragua, which is sovereign over the San
                 Juan River, to determine the appropriate measures to prevent significant
                 transboundary harm or minimize the risk thereof.

                               B. Alleged Breaches of Substantive Obligations
                    174. The Court now turns to the examination of the alleged violations
                 by Costa Rica of its substantive obligations under customary interna-
                 tional law and the applicable international conventions. In particular,
                 Nicaragua claims that the construction of the road caused damage to the
                 San Juan River, which is under Nicaragua’s sovereignty according to the
                 1858 Treaty. Thus, in Nicaragua’s view, Costa Rica breached the obliga-
                 tion under customary international law not to cause significant trans-
                 boundary harm to Nicaragua, the obligation to respect the territorial
                 integrity of Nicaragua and treaty obligations regarding the protection of
                 the environment.
                    175. Over the past four years, the Parties have presented to the Court
                 a vast amount of factual and scientific material in support of their respec-
                 tive contentions. They have also submitted numerous reports and studies
                 prepared by experts and consultants commissioned by each of them on
                 questions such as technical standards for road construction ; river mor-
                 phology ; sedimentation levels in the San Juan River, their causes and
                 effects ; the ecological impact of the construction of the road ; and the
                 status of remediation works carried out by Costa Rica. Some of these
                 specialists have also appeared before the Court to give evidence in their
                 capacity as experts pursuant to Articles 57 and 64 of the Rules of Court.

                    176. It is the duty of the Court, after having given careful consider-
                 ation to all the evidence in the record, to assess its probative value, to
                 determine which facts must be considered relevant, and to draw conclu-
                 sions from them as appropriate. In keeping with this practice, the Court
                 will make its own determination of the facts, on the basis of the totality
                 of the evidence presented to it, and it will then apply the relevant rules of
                 international law to those facts which it has found to be established (Pulp
                 Mills on the River Uruguay (Argentina v. Uruguay), Judgment, I.C.J.
                 Reports 2010 (I), p. 72, para. 168).

                 1. The alleged breach of the obligation not to cause significant transboundary
                    harm to Nicaragua
                    177. Nicaragua claims that the construction works resulted in the
                 dumping of large quantities of sediment into the San Juan River, in par-
                 ticular because Costa Rica’s disregard of basic engineering principles led
                 to significant erosion. For example, Costa Rica carried out extensive
                 deforestation in areas adjacent to the river and earthmoving activities

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                 that led to the creation of unstable cuts and fills in the river’s proximity.
                 Moreover, the road builders left piles of earth exposed to rainfall and
                 failed to construct proper drainage systems and stream crossings so as to
                 avoid erosion. Furthermore, Nicaragua maintains that the stretch of road
                 along the San Juan River is situated too close to the river — nearly half
                 of it was built within 100 metres of the river, and parts of it even within
                 5 metres of the river bank — or on steep slopes, thereby increasing the
                 delivery of sediment to the river. Nicaragua’s main expert opined that
                 erosion is particularly severe in the 41.6 km stretch of the road containing
                 the steepest sections, situated between a point denominated “Marker II”
                 (the western point from which the right bank of the San Juan marks the
                 boundary with Nicaragua) and Boca San Carlos (at the junction of the
                 San Juan and San Carlos Rivers ; see sketch‑map No. 2 above).

                    178. According to Nicaragua, the delivery of these large quantities of
                 sediment to the San Juan River caused an increase in sediment concentra-
                 tions in the river, which are already unnaturally elevated. It argues that
                 this increase, in and of itself, produced harm to the river, as sediment is a
                 pollutant, and that it had a number of adverse effects. First, it brought
                 about changes in the river morphology, as large quantities of the sedi-
                 ment eroded from the road accumulated on the bed of the Lower
                 San Juan, thereby exacerbating the problems for navigation in this stretch
                 of the river and rendering additional dredging necessary to restore the
                 navigability of the channel. Moreover, sediment eroded from the road
                 created large deltas along the Costa Rican bank of the river that obstruct
                 navigation. Secondly, Nicaragua argues that sediment eroded from the
                 road caused harm to the river’s water quality and ecosystem. Thirdly,
                 Nicaragua alleges that the construction of the road has had an adverse
                 impact on tourism and the health of the river’s riparian communities. In
                 addition, Nicaragua maintains that Costa Rica’s continuing failure to
                 comply with road construction standards exposes Nicaragua to future
                 harm, and that Costa Rica has failed to take appropriate remediation
                 measures. Nicaragua further contends that additional risks derive from
                 the possibility of spills of toxic materials into the river, the further devel-
                 opment of the Costa Rican bank of the river and the likelihood of natural
                 disasters caused by adverse events such as hurricanes, tropical storms and
                 earthquakes.
                    179. For its part, Costa Rica argues that the construction of the road
                 has not caused any harm to Nicaragua. According to Costa Rica, erosion
                 is a natural process and sediment is not a pollutant. It contends that
                 Nicaragua has not adduced any evidence of actual harm to the river, let
                 alone significant harm. In addition, Costa Rica argues that the road’s
                 sediment contribution is tiny compared to the river’s existing sediment
                 load. It also recalls that, since 2012, it has carried out remediation works
                 to mitigate erosion at slopes and watercourse crossings (such as slope‑
                 terracing ; digging drainage channels ; installing cross‑drains on the road ;

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                 constructing sediment traps ; and replacing log bridges with modular
                 bridges), with a view to further reducing the quantity of sediment from
                 the road that reaches the San Juan River.

                    180. In order to pronounce on Nicaragua’s allegations, the Court will
                 first address the Parties’ arguments on the contribution of sediment from
                 the road to the river ; then it will examine whether the road‑derived sedi-
                 ment caused significant harm to Nicaragua.
                      (a) The contribution of sediment from the road to the river
                   181. The Parties agree that sediment eroded from the road is delivered
                 to the river, but disagree considerably as to the actual volume.

                    182. Nicaragua argues that the most direct and reliable method to
                 assess the total amount of sediment contributed from the road is to esti-
                 mate the volume of sediment entering the river from all the sites along the
                 road that are subject to erosion. It submits, based on its main expert’s
                 estimates, that the total road‑derived sediment reaching the river amounts
                 to approximately 190,000 to 250,000 tonnes per year, including sediment
                 eroded from the access roads that connect the road to inland areas. Nica-
                 ragua further submits that the volume of sediment in the river due to the
                 construction of the road would increase by a factor of at least ten during
                 a tropical storm or a hurricane.

                    183. Costa Rica challenges the estimates of road‑derived sediment put
                 forward by Nicaragua. In particular, it argues, relying on its main expert’s
                 evidence, that Nicaragua’s experts over‑estimated the areas subject to
                 erosion, which they could not measure directly because the road is in
                 Costa Rica’s territory. It adds that Nicaragua’s estimates are inflated by
                 the inclusion of access roads, which do not contribute any appreciable
                 quantities of sediment to the San Juan River. According to Costa Rica,
                 the sediment contribution from the road is approximately 75,000 tonnes
                 per year. In Costa Rica’s view, even this figure is a significant over‑
                 estimate because it does not take into account the effects of mitigation
                 works recently carried out. Finally, Costa Rica argues that Nicaragua’s
                 experts have overstated the risk of unprecedented rainfall and the impact
                 on sediment loads in the river as a result of hurricanes or tropical storms.

                   184. Costa Rica further points out that the most direct and reliable
                 method for measuring the road’s impact on sediment concentrations in
                 the San Juan River would have been for Nicaragua, which is sovereign
                 over the river, to carry out a sampling programme. Yet Nicaragua has
                 not provided measurements of sedimentation and flow levels in the river.
                 The only empirical data before the Court are two reports of the Nicara-

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                      certain activities and construction of a road (judgment)           729

                 guan Institute of Territorial Studies (INETER), which contain measure-
                 ments of flow rates and suspended sediment concentrations taken at
                 various locations along the San Juan River in 2011 and 2012. Costa Rica
                 argues that neither set of measurements shows any impact from the road.

                    185. Nicaragua replies that a sampling programme would not have
                 been of assistance to assess the impact of the road‑derived sediment
                 because the baseline sediment load of the San Juan prior to the construc-
                 tion of the road is unknown.
                    186. The Court notes that it is not contested that sediment eroded
                 from the road is delivered to the river. As regards the total volume of
                 sediment contributed by the road, the Court observes that the evidence
                 before it is based on modelling and estimates by experts appointed by the
                 Parties. The Court further observes that there is considerable disagree-
                 ment amongst the experts on key data such as the areas subject to erosion
                 and the appropriate erosion rates, which led them to reach different con-
                 clusions as to the total amount of sediment contributed by the road. The
                 Court sees no need to go into a detailed examination of the scientific and
                 technical validity of the different estimates put forward by the Parties’
                 experts. Suffice it to note here that the amount of sediment in the river
                 due to the construction of the road represents at most 2 per cent of the
                 river’s total load, according to Costa Rica’s calculations based on the fig-
                 ures provided by Nicaragua’s experts and uncontested by the latter (see
                 paragraphs 182-183 above and 188-191 below). The Court will come back
                 to this point below (see paragraph 194), after considering further argu-
                 ments by the Parties.

                     Whether the road‑derived sediment caused significant harm to
                 (b)
                     Nicaragua
                    187. The core question before the Court is whether the construction of
                 the road by Costa Rica has caused significant harm to Nicaragua. The
                 Court will begin its analysis by considering whether the fact that the total
                 amount of sediment in the river was increased as a result of the construc-
                 tion of the road, in and of itself, caused significant harm to Nicaragua.
                 The Court will then examine whether such increase in sediment concen-
                 trations caused harm in particular to the river’s morphology, navigation
                 and Nicaragua’s dredging programme ; the water quality and the aquatic
                 ecosystem ; or whether it caused any other harm that may be significant.
                      (i) Alleged harm caused by increased sediment concentrations in the
                          river
                   188. Nicaragua contends that the volume (absolute quantity) of sedi-
                 ment eroded from the road, irrespective of its precise amount, polluted
                 the river thereby causing significant harm to Nicaragua. In Nicaragua’s

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                 view, the impact of the road’s contribution must be considered taking
                 into account the elevated sediment load in the San Juan River which is
                 allegedly due to deforestation and poor land use practices by Costa Rica.
                 An expert for Nicaragua estimated the current sediment load to be
                 approximately 13,700,000 tonnes per year. In this context, Nicaragua
                 submits that there is a maximum load for sediment in the San Juan, and
                 that any additional amount of sediment delivered from the road to the
                 river is necessarily harmful.
                    189. Costa Rica responds that Nicaragua has not shown that the
                 San Juan River has a maximum sediment capacity that has been exceeded.
                 For Costa Rica, the question before the Court is whether the relative
                 impact of the road‑derived sediment on the total load of the San Juan
                 River caused significant harm. Costa Rica claims that it did not. Accord-
                 ing to Costa Rica, the San Juan River naturally carries a heavy sediment
                 load, which is attributable to the geology of the region, and in particular
                 to the occurrence of earthquakes and volcanic eruptions in the drainage
                 area of the river and its tributaries. The volume of sediment contributed
                 by the road is insignificant in the context of the river’s total sediment load
                 (estimated by Costa Rica at 12,678,000 tonnes per year), of which it rep-
                 resents a mere 0.6 per cent at most. The road‑derived sediment is also
                 indiscernible considering the high variability in the river’s sediment loads
                 deriving from other sources. Costa Rica adds that, even if Nicaragua’s
                 figures were to be adopted, the sediment contribution due to the construc-
                 tion of the road would still only represent a small proportion, within the
                 order of 1‑2 per cent, of the total load transported by the San Juan. In
                 Costa Rica’s view, this amount is too small to have any significant impact.
                    190. Nicaragua further argues, drawing on the commentary to the
                 International Law Commission’s Draft Articles on Prevention of Trans-
                 boundary Harm from Hazardous Activities, that any detrimental impact
                 of the construction of the road on the San Juan River need only be sus-
                 ceptible of being measured to qualify as significant harm. Since the
                 amount of sediment in the river due to the construction of the road is
                 measurable, as shown by the fact that both Nicaragua’s and Costa Rica’s
                 experts have estimated its amount, Nicaragua claims that it caused sig-
                 nificant harm.
                    191. Costa Rica retorts that Nicaragua has not shown significant harm
                 by factual and objective standards. It also argues that, even lacking an
                 appropriate baseline, Nicaragua could have measured the impact of the
                 construction of the road on the river’s sediment concentrations by taking
                 its own measurements upstream and downstream of the construction
                 works. However, Nicaragua failed to do so.

                                                       *
                    192. In the Court’s view, Nicaragua’s submission that any detrimental
                 impact on the river that is susceptible of being measured constitutes sig-
                 nificant harm is unfounded. Sediment is naturally present in the river in

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                 large quantities, and Nicaragua has not shown that the river’s sediment
                 levels are such that additional sediment eroded from the road passes a
                 sort of critical level in terms of its detrimental effects. Moreover, the
                 Court finds that, contrary to Nicaragua’s submissions, the present case
                 does not concern a situation where sediment contributed by the road
                 exceeds maximum allowable limits, which have not been determined for
                 the San Juan River. Thus, the Court is not convinced by Nicaragua’s
                 argument that the absolute quantity of sediment in the river due to the
                 construction of the road caused significant harm per se.

                    193. The Court will therefore proceed to consider the relative impact
                 of the road‑derived sediment on the current overall sediment load of the
                 San Juan River. In this regard, the Court notes that the total sediment
                 load of the San Juan River has not been established. Indeed, Nicaragua
                 has not provided direct measurements of sediment levels in the river.
                 Costa Rica, based on its main expert’s report, estimated the river’s total
                 sediment load to be approximately 12,678,000 tonnes per year using mea-
                 surements from the Colorado River. Nicaragua has not provided a com-
                 parable figure, although its expert stated that the current total sediment
                 load of the San Juan River is roughly 13,700,000 tonnes per year.
                    194. On the basis of the evidence before it, and taking into account the
                 estimates provided by the experts of the amount of sediment in the river
                 due to the construction of the road and of the total sediment load of the
                 San Juan River, the Court observes that the road is contributing at
                 most 2 per cent of the river’s total load. It considers that significant harm
                 cannot be inferred therefrom, particularly taking into account the high
                 natural variability in the river’s sediment loads.

                    195. In any event, in the Court’s view, the only measurements that are
                 before it, namely, those contained in the INETER reports from 2011 and
                 2012, do not support Nicaragua’s claim that sediment eroded from the
                 road has had a significant impact on sediment concentrations in the river.
                 A comparison of the measurements taken in 2011, when most of the road
                 had not yet been built, and in 2012, when construction works were under
                 way, shows that sediment levels in the river are variable, and that tribu-
                 taries (particularly the San Carlos and Sarapiquí Rivers) are major
                 sources of sediment for the San Juan. However, the data do not indicate
                 a significant impact on sediment levels from the construction of the road.
                 Moreover, the measurements taken at El Castillo and upstream of Boca
                 San Carlos, which are representative of the steepest stretch of the road,
                 show no significant impact.

                    196. In light of the above, the Court concludes that Nicaragua has not
                 established that the fact that sediment concentrations in the river increased
                 as a result of the construction of the road in and of itself caused signifi-
                 cant transboundary harm.

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                      (ii) Alleged harm to the river’s morphology, to navigation and to
                           Nicaragua’s dredging programme
                   197. The Court will now examine whether the sediment contributed by
                 the road, which the Court has noted corresponds to at most 2 per cent of
                 the river’s average total load, caused any other significant harm. Nicara-
                 gua’s primary argument on the harm caused by the construction of the
                 road concerns the impact of the resulting sediment on the morphology of
                 the river, and particularly on the Lower San Juan.
                   198. The Parties broadly agree that, on the assumption that at “Delta
                 Colorado” 10 per cent of the waters of the San Juan River flow into the
                 Lower San Juan, approximately 16 per cent of the suspended sediments
                 and 20 per cent of the coarse load in the San Juan River would flow into
                 the Lower San Juan. They also concur that, unlike the much larger Colo-
                 rado River, the Lower San Juan has no unfilled capacity to transport
                 sediment. Thus, coarse sediment deposits on the bed of the Lower
                 San Juan. The Parties’ experts further agree that sediment that settles on
                 the riverbed does not spread evenly, but tends to accumulate in shoals
                 and sandbars that may obstruct navigation, especially in the dry season.
                 They disagree, however, on whether and to what extent the finer sus-
                 pended sediments are also deposited on the riverbed and, more broadly,
                 on the effects of the construction of the road on sediment deposition in
                 the Lower San Juan.

                    199. According to Nicaragua’s expert, all of the coarse sediment and
                 60 per cent of the fine sediment contributed by the road to the Lower
                 San Juan settle on the riverbed. To maintain the navigability of the river,
                 Nicaragua is thus required to dredge the fine and coarse sediment that
                 accumulates in the Lower San Juan. In Nicaragua’s view, in a river that is
                 already overloaded with sediment such as the Lower San Juan, any addi-
                 tion of sediment coming from the road causes significant harm to Nicara-
                 gua because it increases its dredging burden. Furthermore, the accumulation
                 of road‑derived sediment reduces the flow of fresh water to the wetlands
                 downstream, which depend on it for their ecological balance.
                    200. Nicaragua also argues that sediment eroded from the road cre-
                 ated “huge” deltas along the river’s channel that obstruct navigation,
                 thereby causing significant harm to Nicaragua.

                    201. Costa Rica responds, relying on the evidence of its main expert,
                 that the aggradation of the Lower San Juan is an inevitable natural phe-
                  nomenon that is unrelated to the construction of the road. For Costa Rica,
                 Nicaragua’s experts also dramatically overestimate the amount of
                  road‑derived sediment that is deposited in the Lower San Juan. First, in
                 Costa Rica’s view, only coarse sediment accumulates on the riverbed,
                 whereas most of the fine sediment is washed into the Caribbean Sea.
                 Secondly, Costa Rica argues that there is no evidence that coarse sediment

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                      certain activities and construction of a road (judgment)            733

                 from the road has actually reached the Lower San Juan. Sediment deposi-
                 tion is not a linear process ; in particular, sediment tends to accumulate in
                 stretches of the river called “response reaches” and may stay there for
                 years before it is transported further down the channel. Moreover,
                 Costa Rica points out that the Parties’ estimates are based on a number
                 of untested assumptions, including estimates of the split of flow and sedi-
                 ment loads between the Colorado River and the Lower San Juan at
                 “Delta Colorado”. Costa Rica further argues that Nicaragua’s case on
                 harm rests on the mistaken assumption that sediment accumulating on
                 the bed of the Lower San Juan will necessarily need to be dredged.

                    202. As to the deltas along the Costa Rican bank of the river,
                 Costa Rica argues that Nicaragua has not shown that they were created
                 as a result of the construction of the road. For example, satellite imagery
                 demonstrates that at least two of these deltas pre‑date the road. Costa Rica
                 further points out that similar deltas exist on the Nicaraguan bank of the
                 river. In any event, their impact on the morphology of the river and on
                 navigation is insignificant because of their small size relative to the width
                 of the river.

                                                      *
                    203. The Court notes that Nicaragua has produced no direct evidence
                 of changes in the morphology of the Lower San Juan or of a deteriora-
                 tion of its navigability since the construction of the road began. Nicara-
                 gua’s case once again rests on modelling and estimates by its experts,
                 which have not been substantiated by empirical data. The Court observes
                 in this regard that there are considerable uncertainties concerning the vol-
                 ume of sediment eroded from the road that has allegedly reached the
                 Lower San Juan and deposited on its bed. For example, Nicaragua has
                 not adduced scientific evidence on the division of flow and sediment loads
                 at “Delta Colorado”, but based its estimates on a report of the Costa Rican
                 Institute of Electricity, which is in turn based on measurements taken
                 only in the Colorado River.

                    204. The Court further considers that the expert evidence before it
                 establishes that the accumulation of sediment is a long‑standing natural
                 feature of the Lower San Juan, and that sediment delivery along the San
                 Juan is not a linear process. The road‑derived sediment is one of a num-
                 ber of factors that may have an impact on the aggradation of the Lower
                 San Juan. The Court therefore considers that the evidence adduced by
                 Nicaragua does not prove that any morphological changes in the Lower
                 San Juan have been caused by the construction of the road in particular.

                   205. As to Nicaragua’s claim that the construction of the road has had
                 a significant adverse impact on its dredging burden, the Court notes that

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                 Nicaragua has adduced no evidence of an increase in its dredging activi-
                 ties due to the construction of the road. In this connection, the Court also
                 recalls that Nicaragua initiated its dredging programme before the con-
                 struction of the road started (see paragraphs 63‑64 above). In any event,
                 the Court recalls its conclusion that the construction of the road has
                 caused an increase in sediment concentrations in the river corresponding
                 to at most 2 per cent (see paragraph 194 above). The Court observes that
                 there is no evidence that sediment due to the construction of the road is
                 more likely to settle on the riverbed than sediment from other sources.
                 Thus, sediment coming from the road would correspond to at
                 most 2 per cent of the sediment dredged by Nicaragua in the Lower
                 San Juan. The Court is therefore not convinced that the road‑derived
                 sediment led to a significant increase in the bed level of the Lower
                 San Juan or in Nicaragua’s dredging burden.

                   206. Finally, the Court turns to Nicaragua’s claim that the sediment
                 deltas along the Costa Rican bank of the river have caused significant
                 harm to the river’s morphology and to navigation. In the Court’s view,
                 the photographic evidence adduced by Nicaragua indicates that there are
                 deltas on the Costa Rican bank of the river to which the construction of
                 the road is contributing sediment. The Court observes that Nicaragua
                 submitted that in the steepest stretch of the road there are eight “huge”
                 deltas but was not able to specify the total number of deltas allegedly cre-
                 ated as a consequence of the construction of the road. The Court further
                 notes that satellite images in the record show that at least two of these
                 deltas pre‑date the road. In any event, the Court considers that Nicara-
                 gua has not presented sufficient evidence to prove that these deltas, which
                 only occupy the edge of the river’s channel on the Costa Rican bank,
                 have had a significant adverse impact on the channel’s morphology or on
                 navigation.

                   207. For the foregoing reasons, the Court concludes that Nicaragua
                 has not shown that sediment contributed by the road has caused signifi-
                 cant harm to the morphology and navigability of the San Juan River and
                 the Lower San Juan, nor that such sediment significantly increased Nica-
                 ragua’s dredging burden.
                      (iii) Alleged harm to water quality and the aquatic ecosystem

                    208. The Court will now consider Nicaragua’s contention concerning
                 harm to water quality and the aquatic ecosystem. In its written pleadings,
                 Nicaragua alleged that the increased sediment concentrations in the river
                 as a result of the construction of the road caused significant harm to fish
                 species, many of which belong to families that are vulnerable to elevated
                 levels of sediments, to macro‑invertebrates and to algal communities in
                 the river. Furthermore, according to Nicaragua, the road’s sediment

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                      certain activities and construction of a road (judgment)           735

                 caused a deterioration in the water quality of the river. To prove harm to
                 aquatic organisms and water quality, Nicaragua relied inter alia on an
                 expert report based on sampling at 16 deltas in the river, which concluded
                 that both species richness and abundance of macro‑invertebrates were
                 significantly lower on the south bank than on the north bank.

                    209. During the course of the oral proceedings, Nicaragua’s case
                 shifted from its prior claim of actual harm to the river’s ecosystem to a
                 claim based on the risk of harm. The Parties now agree that there have
                 been no studies of the fish species in the San Juan River to determine
                 whether they are vulnerable to elevated levels of sediment. However,
                 Nicaragua claims that Costa Rica’s Environmental Diagnostic Assess-
                 ment and the follow‑up study carried out in January 2015 by the Tropical
                 Science Centre (hereinafter “CCT”, by its Spanish acronym) show that
                 the road is harming macro‑invertebrates and water quality in the tributar-
                 ies that flow into the San Juan River. The CCT measured water quality in
                 Costa Rican tributaries upstream and downstream of the road and
                 recorded a lower water quality downstream of the road. For Nicaragua,
                 this demonstrates a risk of harm to the river itself due to the cumulative
                 impact of those tributaries.

                    210. For Costa Rica, Nicaragua’s case on the impact on fish species
                 fails due to the lack of evidence of actual harm. Relying on one of its
                 experts, Costa Rica argues that it is very likely that species living in the
                 river are adapted to conditions of high and variable sediment loads and
                 are highly tolerant of such conditions. As to macro‑invertebrates and
                 water quality, Costa Rica submits that the CCT study shows no signifi-
                 cant impact. In any event, its results are based on sampling on small trib-
                 utary streams in Costa Rica, and cannot be transposed to the much larger
                 San Juan River. Costa Rica further argues that the expert report adduced
                 by Nicaragua does not provide sufficient support for Nicaragua’s claim
                 that the construction of the road has had an adverse impact on
                 macro‑invertebrates living in deltas along the south bank of the river.

                                                      *
                    211. The Court observes that Nicaragua has not presented any evi-
                 dence of actual harm to fish in the San Juan River, nor has it identified
                 with precision which species of fish have allegedly been harmed by the
                 construction of the road.
                    212. In the Court’s view, the Environmental Diagnostic Assessment
                 relied upon by Nicaragua only shows that the construction of the road

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                 has had a localized impact on macro‑invertebrate communities and water
                 quality in small Costa Rican streams draining into the San Juan River.
                 However, the Court is not persuaded that the results of the Environmen-
                 tal Diagnostic Assessment and the follow‑up study can be transposed to
                 the San Juan River, which has an average width of nearly 300 metres. As
                 regards the expert report submitted by Nicaragua, the Court finds it dif-
                 ficult to attribute any differences in macro‑invertebrate richness and
                 abundance between the north and the south banks of the river to the
                 construction of the road alone, as opposed to other factors such as the
                 size of the catchment area and the nutrient levels therein.

                    213. On the basis of the foregoing considerations, the Court finds that
                 Nicaragua has not proved that the construction of the road caused sig-
                 nificant harm to the river’s ecosystem and water quality.
                      (iv) Other alleged harm
                    214. Nicaragua also alleges that the construction of the road has had
                 an adverse impact on the health of the communities along the river, which
                 is dependent upon the health of the river itself. Furthermore, in Nicara-
                 gua’s view, the road significantly affected the area’s tourism potential as
                 it has a negative visual impact on the natural landscape. Finally, Nicara-
                 gua argues that, in addition to the transboundary harm that the road has
                 already caused, it poses a significant risk of future transboundary harm.
                 According to Nicaragua, additional risks derive from the possibility
                 of spills of toxic materials into the river whenever hazardous substances
                 are transported on the road, and from any further development of the
                 right bank of the river, such as increased agricultural and commercial
                 activities.
                    215. Costa Rica responds that Nicaragua did not adduce any evidence
                 of actual impact on tourism or on the health of riparian communities.
                 Moreover, it did not explain the legal basis of its claims. Furthermore,
                 Costa Rica contends that Nicaragua’s arguments on the risk of toxic
                 spills in the river are based entirely on speculation : Costa Rica’s 1995
                 Regulations for the Ground Transportation of Hazardous Material pro-
                 vide that hazardous substances can only be transported on authorized
                 roads, and Route 1856 is not one of them.

                                                     *
                    216. The Court finds that Nicaragua did not substantiate its conten-
                 tions regarding harm to tourism and health. The Court further observes
                 that Nicaragua’s arguments concerning the risk of toxic spills into the
                 river and of further development of the Costa Rican bank of the river are
                 speculative and fail to show any harm. Therefore, these arguments fail.

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                      (c) Conclusion
                    217. In light of the above, the Court concludes that Nicaragua has not
                 proved that the construction of the road caused it significant transbound-
                 ary harm. Therefore, Nicaragua’s claim that Costa Rica breached its sub-
                 stantive obligations under customary international law concerning
                 transboundary harm must be dismissed.

                 2. Alleged breaches of treaty obligations
                    218. Nicaragua further argues that Costa Rica violated substantive
                 obligations contained in several universal and regional instruments. First,
                 it contends that Costa Rica breached Article 3, paragraph 1, of the
                 Ramsar Convention. Secondly, it argues that Costa Rica acted contrary
                 to the object and purpose of the 1990 Agreement over the Border Pro-
                 tected Areas between Nicaragua and Costa Rica (“SI‑A‑PAZ Agree-
                 ment”). Thirdly, Nicaragua alleges that, by its activities, Costa Rica
                 violated Articles 3 and 8 of the Convention on Biological Diversity.
                 Fourthly, it claims that Costa Rica violated several provisions of the
                 Convention for the Conservation of the Biodiversity and Protection of
                 Priority Wilderness Areas in Central America. Fifthly, it alleges viola-
                 tions of the Central American Convention for the Protection of the Envir
                 onment and the Tegucigalpa Protocol to the Charter of the Organization
                 of Central American States. Finally, Nicaragua contends that Costa Rica
                 breached Article 3 of the Regional Agreement on the Transboundary
                 Movement of Hazardous Wastes, on the ground that it did not adopt and
                 implement the precautionary approach to pollution problems provided
                 for in that instrument.

                    219. In response to these allegations, Costa Rica argues at the outset
                 that, since Nicaragua failed to prove that the construction of the road
                 caused any significant transboundary harm, its contentions must fail.
                 Costa Rica further points out that the construction of the road does not
                 touch upon protected Nicaraguan wetlands falling within the Ramsar
                 Convention. Moreover, it states that Nicaragua has identified no provi-
                 sion of the SI‑A‑PAZ Agreement that was allegedly breached. Costa Rica
                 further maintains that the Central American Convention for the Protec-
                 tion of the Environment and the Tegucigalpa Protocol are of no relevance
                 to the present dispute and that there is no factual basis for Nicaragua’s
                 contentions regarding the Regional Agreement on the Transboundary
                 Movement of Hazardous Wastes.

                                                      *
                   220. The Court notes that both Nicaragua and Costa Rica are parties
                 to the instruments invoked by Nicaragua. Irrespective of the question of
                 the binding character of some of the provisions at issue, the Court

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                 observes that, in relation to these instruments, Nicaragua simply makes
                 assertions about Costa Rica’s alleged violations and does not explain how
                 the “objectives” of the instruments or provisions invoked would have
                 been breached, especially in the absence of proof of significant harm to
                 the environment (see paragraph 217 above). The Court therefore consid-
                 ers that Nicaragua failed to show that Costa Rica infringed the
                 above‑mentioned instruments.

                 3. The obligation to respect Nicaragua’s territorial integrity and sovereignty
                   over the San Juan River
                    221. Nicaragua further alleges that the deltas created by sediment
                 eroded from the road are “physical invasions, incursions by Costa Rica
                 into Nicaragua’s sovereign territory . . . through the agency of sediment”
                 and that their presence constitutes “trespass” into Nicaragua’s territory.
                 Moreover, Nicaragua maintains that the dumping of sediments, soil,
                 uprooted vegetation and felled trees into the river by Costa Rica poses a
                 serious threat to the exercise of Nicaragua’s right of navigation on the
                 San Juan, which is based on its sovereignty over the river. Nicaragua
                 therefore claims that, by its conduct and activities, Costa Rica violated
                 Nicaragua’s territorial integrity and sovereignty over the San Juan River,
                 as established by the 1858 Treaty.

                    222. Costa Rica argues that undertaking road infrastructure works
                 entirely within its territory does not infringe the boundary delimited by
                 the 1858 Treaty or violate Nicaragua’s sovereignty, nor does it affect
                 Nicaragua’s right to navigate the San Juan River. Furthermore,
                 Costa Rica maintains that the 1858 Treaty has no bearing on this case, as
                 it does not regulate the issues that are at stake here.

                    223. The Court considers that, whether or not sediment deltas are cre-
                 ated as a consequence of the construction of the road, Nicaragua’s theory
                 to support its claim of a violation of its territorial integrity via sediment
                 is unconvincing. There is no evidence that Costa Rica exercised any
                 authority on Nicaragua’s territory or carried out any activity therein.
                 Moreover, for the reasons already expressed in paragraphs 203 to 207
                 above, Nicaragua has not shown that the construction of the road
                 impaired its right of navigation on the San Juan River. Therefore, Nica-
                 ragua’s claim concerning the violation of its territorial integrity and sov-
                 ereignty must be dismissed.

                                                C. Reparation
                   224. Nicaragua requests the Court to adjudge and declare that, by its
                 conduct, Costa Rica has breached its obligation not to violate Nicara-
                 gua’s territorial integrity ; its obligation not to damage Nicaraguan terri-

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                 tory ; and its obligations under general international law and the relevant
                 environmental treaties (final submissions, para. 1 ; see paragraph 52
                 above).
                   In the light of its reasoning above, the Court’s declaration that
                 Costa Rica violated its obligation to conduct an environmental impact
                 assessment is the appropriate measure of satisfaction for Nicaragua.

                    225. Secondly, Nicaragua asks the Court to order that Costa Rica
                 “[c]ease all its continuing internationally wrongful acts that affect or are
                 likely to affect the rights of Nicaragua” (ibid., para. 2 (i)).

                   The Court considers that Costa Rica’s failure to conduct an environ-
                 mental impact assessment does not at present adversely affect the rights
                 of Nicaragua nor is it likely further to affect them. Consequently, there
                 are no grounds to grant the remedy requested.

                    226. Thirdly, Nicaragua requests the Court to order Costa Rica to
                 restore to the extent possible the situation that existed before the road
                 was constructed, and to provide compensation for the damage caused
                 insofar as it is not made good by restitution (ibid., para. 2 (ii) and (iii)).
                 The Court recalls that restitution and compensation are forms of repara-
                 tion for material injury. The Court notes that, although Costa Rica did
                 not comply with the obligation to conduct an environmental impact
                 assessment, it has not been established that the construction of the road
                 caused significant harm to Nicaragua or was in breach of other substan-
                 tive obligations under international law. As such, restoring the original
                 condition of the area where the road is located would not constitute an
                 appropriate remedy for Costa Rica’s breach of its obligation to carry out
                 an environmental impact assessment (see Pulp Mills on the River Uruguay
                 (Argentina v. Uruguay), Judgment, I.C.J. Reports 2010 (I), p. 103,
                 para. 271). For the same reasons, the Court declines to grant Nicaragua’s
                 claim for compensation.
                    In view of Nicaragua’s failure to prove that significant harm was
                 caused, the Court does not need to consider the appointment of an expert
                 or committee to evaluate the extent of harm and the chain of causation,
                 as Nicaragua suggests.
                    227. The Court further considers that Nicaragua’s request to order
                 Costa Rica not to undertake any future development in the border area
                 without an appropriate environmental impact assessment (final submis-
                 sions, para. 3 (i)) must be rejected. As the Court stated in paragraph 173
                 above, Costa Rica’s obligation to conduct an environmental impact
                 assessment only applies to activities carrying a risk of significant trans-
                 boundary harm, and there is no reason to suppose that Costa Rica will
                 not comply with its obligations under international law, as outlined in
                 this Judgment, as it conducts any future activities in the area, including
                 further construction works on the road.

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                    228. To conclude, the Court notes that Costa Rica has begun mitiga-
                 tion works in order to reduce the adverse effects of the construction of the
                 road on the environment. It expects that Costa Rica will continue to pur-
                 sue these efforts in keeping with its due diligence obligation to monitor
                 the effects of the project on the environment. It further reiterates the
                 value of ongoing co‑operation between the Parties in the performance of
                 their respective obligations in connection with the San Juan River.

                                                           *
                                                       *       *

                      229. For these reasons,
                      The Court,
                      (1) By fourteen votes to two,
                   Finds that Costa Rica has sovereignty over the “disputed territory”, as
                 defined by the Court in paragraphs 69‑70 of the present Judgment ;
                      in favour : President Abraham ; Vice‑President Yusuf ; Judges Owada,
                        Tomka, Bennouna, Cançado Trindade, Greenwood, Xue, Donoghue,
                        Gaja, Sebutinde, Bhandari, Robinson ; Judge ad hoc Dugard ;

                      against : Judge Gevorgian ; Judge ad hoc Guillaume ;
                      (2) Unanimously,
                   Finds that, by excavating three caños and establishing a military pres-
                 ence on Costa Rican territory, Nicaragua has violated the territorial sov-
                 ereignty of Costa Rica ;
                      (3) Unanimously,
                   Finds that, by excavating two caños in 2013 and establishing a military
                 presence in the disputed territory, Nicaragua has breached the obligations
                 incumbent upon it under the Order indicating provisional measures issued
                 by the Court on 8 March 2011 ;
                      (4) Unanimously,
                   Finds that, for the reasons given in paragraphs 135‑136 of the present
                 Judgment, Nicaragua has breached Costa Rica’s rights of navigation on
                 the San Juan River pursuant to the 1858 Treaty of Limits ;
                      (5) (a) Unanimously,
                   Finds that Nicaragua has the obligation to compensate Costa Rica for
                 material damages caused by Nicaragua’s unlawful activities on
                 Costa Rican territory ;

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                      (b) Unanimously,
                    Decides that, failing agreement between the Parties on this matter
                 within 12 months from the date of this Judgment, the question of com-
                 pensation due to Costa Rica will, at the request of one of the Parties, be
                 settled by the Court, and reserves for this purpose the subsequent proce-
                 dure in the case concerning Certain Activities Carried Out by Nicaragua in
                 the Border Area (Costa Rica v. Nicaragua) ;
                      (c) By twelve votes to four,
                   Rejects Costa Rica’s request that Nicaragua be ordered to pay costs
                 incurred in the proceedings ;
                      in favour : President Abraham ; Vice‑President Yusuf ; Judges Owada, Ben-
                         nouna, Cançado Trindade, Xue, Donoghue, Gaja, Bhandari, Robinson,
                         Gevorgian ; Judge ad hoc Guillaume ;
                      against : Judges Tomka, Greenwood, Sebutinde ; Judge ad hoc Dugard ;

                      (6) Unanimously,
                    Finds that Costa Rica has violated its obligation under general interna-
                 tional law by failing to carry out an environmental impact assessment
                 concerning the construction of Route 1856 ;

                      (7) By thirteen votes to three,
                      Rejects all other submissions made by the Parties.
                      in favour : President Abraham ; Vice‑President Yusuf ; Judges Owada,
                        Tomka, Bennouna, Cançado Trindade, Greenwood, Xue, Donoghue,
                        Gaja, Sebutinde, Gevorgian ; Judge ad hoc Guillaume ;
                      against : Judges Bhandari, Robinson ; Judge ad hoc Dugard.

                   Done in French and in English, the French text being authoritative, at
                 the Peace Palace, The Hague, this sixteenth day of December, two thou-
                 sand and fifteen, in three copies, one of which will be placed in the
                 archives of the Court and the others transmitted to the Government of
                 the Republic of Costa Rica and the Government of the Republic of Nica-
                 ragua, respectively.

                                                               (Signed) Ronny Abraham,
                                                                           President.
                                                              (Signed) Philippe Couvreur,
                                                                            Registrar.

                   Vice‑President Yusuf appends a declaration to the Judgment of the
                 Court ; Judge Owada appends a separate opinion to the Judgment of the
                 Court ; Judges Tomka, Greenwood, Sebutinde and Judge ad hoc

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                 Dugard append a joint declaration to the Judgment of the Court ; Judge
                 Cançado Trindade appends a separate opinion to the Judgment of the
                 Court ; Judge Donoghue appends a separate opinion to the Judgment of
                 the Court ; Judge Bhandari appends a separate opinion to the Judgment
                 of the Court ; Judge Robinson appends a separate opinion to the
                 Judgment of the Court ; Judge Gevorgian appends a declaration to the
                  Judgment of the Court ; Judge ad hoc Guillaume appends a declaration
                  to the Judgment of the Court ; Judge ad hoc Dugard appends a separate
                 opinion to the Judgment of the Court.

                                                                    (Initialled) R.A.
                                                                    (Initialled) Ph.C.

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