The codification operation that led to the adoption of the United Nations Convention on the Law of the Sea<fnref n="2" /> (hereafter “*UNCLOS*”) in 1982 contributed to the structure of international relations in the use of the seas and oceans. Considered for a long time as “a body of customary international law”,<fnref n="3" /> the rules governing the seas were becoming obsolete with time and “the need for adaptability”<fnref n="4" /> became the most important concern of the international community. Therefore, there was a significant change in the rules governing the use of the sea<fnref n="5" />, especially concerning the duty of States to cooperate. The reading of the *UNCLOS* preamble suggests cooperation is at the heart of sea use. In fact, states wanted to settle, in the spirit of mutual understanding and cooperation, all issues relating to the law of the sea. The same observation goes for international rules relating to treaties, notably the 1969 Vienna Convention on the Law of Treaties.<fnref n="6" /> In its preamble, treaties constitute a means of developing peaceful cooperation among the Nations. It is worth noting that one of the purposes of the United Nations is to achieve international cooperation, in solving international problems.<fnref n="7" /> International cooperation is the “guiding principle of the United Nations.”<fnref n="8" /> In addition, the Charter of Economic Rights and Duties of States<fnref n="9" /> imposes cooperation as the main mechanism for resolving States’ economic and social problems; and encourages cooperation, based on mutual advantage and equitable benefits for all peace-loving States.<fnref n="10" /> From the combined reading of these international instruments, cooperation is the most important means of international relations. International cooperation *sensu largo* is

> Cooperation that two or more States may grant each other by agreement or on a case-by-case basis, [in various] matters, for the transmission, reciprocal recognition and/or enforcement of foreign legal acts and judgements, for the transmission of information, for the transfer of arrested persons (extradition, mutual assistance in criminal matters, transfer of detainees), for the performance of investigations, letters rogatory and searches for missing persons.<fnref n="11" />

The school of liberal institutionalism reminds us that there is a time when cooperation can be advantageous for States.<fnref n="12" /> Since all States have interests in the seas, cooperation is the main vehicle for such interests protection. The *UNCLOS* aimed the realization of a just and equitable international economic order taking account of interests and needs of mankind as a whole and, in particular, the special interests and needs of developing coastal or land-locked countries.<fnref n="13" /> While the principal role of the law of the sea is the reconciliation of States’ interests, “the protection of community interests appears at present to be increasingly important in th[is] law.”<fnref n="14" /> Even though positive international law remains to some extent the law of States, these States not only have individual interests, but also – and increasingly – share interests that are common to all States, as well as to their (trans)national communities.<fnref n="15" /> Such a development is acknowledged by the “widely referenced move away from an international ‘law of coexistence’ towards a ‘law of cooperation’.”<fnref n="16" /> In effect, the obligation of States to cooperate is not merely the concern of law of the sea, but also other areas of international law like international criminal law,<fnref n="17" /> international environmental law,<fnref n="18" /> etc. By making cooperation an obligation of States in their relations, international law imposes on them peaceful participation in international development. In this respect, there is a promotion of pacific settlement of disputes<fnref n="19" /> amongst States as the primary mechanism imposed on them under international law whatever their matter. The origin of duty to cooperate under *UNCLOS* can be found in Principle 7 of the *Rio Declaration on Environment and Development*, which states: “States shall co-operate in a spirit of global partnership to conserve, protect and restore the health and integrity of the Earth’s ecosystem.”<fnref n="20" /> The duty to cooperate is a legal requirement imposed on *UNCLOS* Parties to proactively work together in a coordinated manner as far as the law of the sea is concerned, taking into account both the individual State and community interests. This obligation includes:

> an obligation to notify affected States of actual or imminent danger to the marine environment, to make contingency plans for dealing with such dangers, to research, to study and to exchange information and data in order to provide scientific criteria for the development of rules, standards, procedures and practices to reduce, prevent or control pollution.<fnref n="21" />

The obligation to cooperate is a corollary of the principle of performance in good faith of States’ treaty obligations. The principle of good faith is a source of the duty to cooperate in general international law.<fnref n="22" /> Article 300 of *UNCLOS* requires States Parties to fulfil in good faith the obligations assumed under the Convention. The International Court of Justice (ICJ) in the North Sea Continental Shelf Cases specified the content of the international obligation to cooperate in a spirit of good faith:

> The parties are under an obligation to enter into negotiations with a view to arriving at an agreement, and not merely to go through a formal process of negotiation […]; they are under an obligation so to conduct themselves that the negotiations are meaningful, which will not be the case when either of them insists upon its own position without contemplating any modification of it.<fnref n="23" />

As noted by Rogoff, “[t]he international negotiation process, viewed as a whole, is the principal vehicle for cooperation between states.”<fnref n="24" /> Like a contract, *UNCLOS* is an instrument of cooperation in the maritime field.<fnref n="25" /> Therefore, the parties shall come together to fulfil their obligations following the decision they have made, taking into account the interests of each of them. In that regard, all States concerned negotiate piecemeal and approve all relevant decisions unanimously, whether separately or within a collegiate body. Institutionalized cooperation is more successful in preparing the necessary data for decision-makers.<fnref n="26" /> Here, the principle of reciprocity<fnref n="27" /> plays an important role since States ensure themselves that their relations are moving smoothly in keeping with the principle of good faith. As the main actors to whom the duty to cooperate applies, States must respect all the rules of international law in the conduct of their sea-related relations. The performance of the duty to cooperate implies the application of the principle of limited sovereignty. The concept of sovereignty in international law is a crucial element for identifying the State endowed with the ability to enter treaties.<fnref n="28" /> Despite the complexity of the concept, De Malberg considered that a State is sovereign when it is free from any subordination to a foreign power from an international perspective.<fnref n="29" /> Combacau considers sovereignty as the freedom of the State to do everything in its power.<fnref n="30" /> Nonetheless, when the State becomes a party to a treaty, it decides to abandon part of its sovereignty to give legitimacy to the instrument. In effect, the States Parties in application of the principle *pacta sunt servanda*<fnref n="31" /> must perform the duty of cooperation imposed by *UNCLOS*.

Cooperation is evoked almost in two-thirds<fnref n="32" /> of the *UNCLOS*, either as general cooperation or the duty to cooperate. Direct obligations are imposed on States, which concern all parts of the sea.<fnref n="33" /> This paper assesses the nature and scope of the obligation of States to cooperate under *UNCLOS*. The authors undertake to analyse in a detailed manner the relevant *UNCLOS*provisions to determine the nature of the obligation incumbent on States Parties concerning cooperation. On the other hand, they dwell on the uncertainty surrounding the performance of this obligation to study its hindrances.

<footnote n="2">Yoshifumi Tanaka, *The International Law of the Sea*, 3rd ed (Cambridge: Cambridge University Press, 2019) at 26.</footnote>

<footnote n="3">*Ibid*.</footnote>

<footnote n="4">The three conferences for the codification of the law of the sea [*UNCLOS* I (1958), *UNCLOS* II (1960), and *UNCLOS* III (1973-1982)] focused on the issues of the delimitation of the sea and the determination of the jurisdiction of costal States over the parts of the sea placed under their jurisdiction.</footnote>

<footnote n="5">*Vienna Convention on the Law of Treaties*, 23 May 1969, 1155 UNTS 331 [*VCLT*].</footnote>

<footnote n="6">*UN Charter*, 26 June 1945, UNTS No 1 Chapter XVI, art 1(3).</footnote>

<footnote n="7">Anne Peters, “International Dispute Resolution: A Network of Cooperational Duties” (2003) 14:1 EJIL 1 at 2. See *UN Charter*, arts 1(3); 11; 13; Chapter IX.</footnote>

<footnote n="8">*Charter of Economic Rights and Duties of States*, UNGA, 29th Sess, UN Doc A/9631 (1974) GA Res 3281 (XXIX).</footnote>

<footnote n="9">*Ibid*, Preamble.</footnote>

<footnote n="10">See Jean Salmon, *Dictionnaire de droit international public* (Bruxelles: Bruylant/AUF, 2001) at 432.</footnote>

<footnote n="11">See Bertrand Badie, “Les Nations Unies face au conservatisme des grandes puissances”, *Le Monde diplomatique* (June 2015) at 9.</footnote>

<footnote n="12">*UNCLOS*, *supra* note 1, Preamble.</footnote>

<footnote n="13">See Tanaka, *International Law of the Sea*, *supra*note 2, at 538.</footnote>

<footnote n="14">See Rozemarijn J Roland Holst, *Change in the Law of the Sea: Context, Mechanisms and Practice* (Leiden/Boston: Brill Nijhoff, 2022), at 59.</footnote>

<footnote n="15">*Ibid.*</footnote>

<footnote n="16">See generally Valerie Oosterveld, Mike Perry & John McManus, “The cooperation of States with the International Criminal Court” (2001) 25:3 Fordham Intl L J 767.</footnote>

<footnote n="17">See generally Alastair Neil Clark, “The Duty to Cooperate in International Environmental Law: Constraining State Discretion through Due Respect” (May 2020), online: <https://academic.oup.com/yielaw/article/30/1/22/6054286>.</footnote>

<footnote n="18">See *UN Charter*, Chapter VI.</footnote>

<footnote n="19">*Rio Declaration on Environment and Development*, Annex I of the *Report of the United Nations Conference on Environment and Development*, UNGA, 1992, UN Doc A/CONF.151/26 (Vol 1), Principle 7.</footnote>

<footnote n="20">See Moira L McConnell & Edgar Gold, “The Modem Law of the Sea: Framework for the Protection and Preservation of the Marine Environment? (1991) 23:1 Case Western Reserve J of Intl L 83 at 91.</footnote>

<footnote n="21">See Peters, “International Dispute Resolution”, *supra*note 7 at 15-16.</footnote>

<footnote n="22">*North Sea Continental Shelf (Federal Republic of Germany/Denmark; Federal Republic of Germany/Netherlands)*, Judgment of 20 February 1969, [1969] ICJ Rep 3, para 85.</footnote>

<footnote n="23">Martin A Rogoff, “The Obligation to Negotiate in International Law: Rules and Realities” (1994) 16:1 Mich J of Intl L 141 at 182.</footnote>

<footnote n="24">René Demogue, Georges Ripert and Jean Carbonnier have defended the idea that the contract is fundamentally an act of cooperation. On this subject, read François Diesse, “Le devoir de coopération comme principe directeur du contrat” (1999) 43 Arch Phil D 259.</footnote>

<footnote n="25">Dante A Caponera, “Patterns of Cooperation in International Water Law: Principles and Institutions” (1985) 25:3 Nat Resources J 563 at 570.</footnote>

<footnote n="26">Read Francisco Paris & Nita Ghei, “The Role of Reciprocity in International Law” (2003) 36:1 Cornell Intl L J 93.</footnote>

<footnote n="27">The Permanent International Court of Justice (PCIJ) stated, “the right of entering into international engagements is an attribute of State sovereignty.” See *SS Wimbledon*case, PCIJ, Series A, No 1, Judgment 17 August 1923, at 25.</footnote>

<footnote n="28">Raymond Carré de Malberg, *Contribution à la théorie générale de l’État: spécialement d’après les* *données fournies par le droit constitutionnel français,* vol 1 (Paris: Recueil Sirey, 1920) at 75.</footnote>

<footnote n="29">Jean Combacau, “Pas une puissance, une liberté : la souveraineté internationale des États” (1993) 67 Pouvoirs at 51.</footnote>

<footnote n="30">See *VCLT*, art 26.</footnote>

<footnote n="31">Christophe Nouzha notes that cooperation underpins all the rules of law enshrined in the *UNCLOS*. See Christophe Nouzha, “Le rôle du Tribunal international du droit de la mer dans la protection du milieu marin” (2005) 8:2 RQDI 65 at 81.</footnote>

<footnote n="32">Read United Nations, Division for Ocean Affairs and the Law of the Sea (Office of Legal Affairs), *The Obligations of States Parties under the United Nations Convention on the Law of the Sea and Complementary Instrument,*New York, 2004.</footnote>

<footnote n="33">Seokwoo Lee, “*UNCLOS* and the Obligation to Cooperate”, in Clive Schofield, ed, *Maritime Energy Resources in Asia: Legal Regimes and Cooperation* (February 2012) Special Report No 37 at 25.</footnote>
# ***

The foregoing assessment of the nature and scope of the States obligation to cooperate under *UNCLOS* leads to the following inferences. The multiplicity of relevant provisions in this instrument and the diversity of semantics used give rise to a complex set of duties. This paper found that the obligation of States to cooperate is intricate. Sometimes the *Convention* prescribes a mandatory obligation to cooperate; sometimes it simply urges States to cooperate. It even provides for cases where cooperation is simply optional for States. Adopting a broad conception of the obligation to cooperate, this paper included the obligation to exchange information and the obligation to negotiate or consult. In this respect, the obligation to cooperate has a tricky nature. Then again, the obligation to exchange information is complex because it includes two binding sub-obligations: the obligation of publicity and the obligation to notify. On the other hand, there is an ambivalent obligation to negotiate or consult.

The semantic diversity of *UNCLOS* with regard to the States’ obligation to cooperate constitutes a hindrance to the performance of this obligation, as this paper demonstrated. The proposed solution to this limitation is the performance in good faith. Another hindrance is the pursuit of special States’ interests. To overcome this limitation, States need awareness on the fact that the protection of community interests can help preserve their individual interests. The final limitation is the paucity of coercive measures against States. In this respect, though *UNCLOS* does not contemplates such measures against States, the latter may resort to countermeasures to induce compliance with the *Convention*. As D’Amato notes, “the nations of the world are in legal equilibrium” in such a way that “an encroachment by any State upon the rights of another State or States should immediately trigger their threat or use of reprisals.”<fnref n="180" /> Therefore, despite the apparent flexibility of its cooperation regime, States, as masters of international normativity, have the power to turn *UNCLOS* into a coercive order.