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USINDOPACOM J06/SJA TACAID SERIES

TOPIC: DEFENSE OF GUAM AND THE COMMONWEALTH 

OF THE NORTHERN MARIANA ISLANDS (CNMI)

BLUF

 USINDOPACOM's priority mission is to defend the U.S. homeland.

 The U.S. Territories of Guam and CNMI are part of the U.S. homeland and indistinguishable from the fifty states 

for purposes of defense under international and domestic law. 

 The U.N. Charter’s prohibition on the threat or use of force against the territorial integrity or political 

independence of any state applies with respect to all U.S. territory including Guam and CNMI. 

 As such, the United States has an inherent right under international law to exercise self-defense if Guam or CNMI 

is subject to an actual or imminent armed attack. The United States may also take necessary and proportionate 

countermeasures against internationally unlawful actions directed against Guam or CNMI.

 USINDOPACOM has an enduring obligation to defend the U.S. homeland – this TACAID addresses the legal 

foundation that underpins that defense obligation with respect to the territory and people of Guam and CNMI. 

WHY THIS MATTERS

 As the most forward U.S. territories in the Pacific, Guam and CNMI are critical to U.S. defense and power 

projection.

i The Guam Defense System is COMUSINDOPACOM’s top homeland defense priority.ii

 USINDOPACOM’s initiative to stand-up Joint Task Force (JTF) Micronesia – forward-stationed in Guam – reflects 

Guam’s importance as a command and control node for operations and activities across the Guam cluster (Guam, 

CNMI, Wake Island, and Midway Island and the Freely Associated States).iii 

 Guam and CNMI are home to over 200,000 U.S. citizens; vibrant cultures; international tourism and investment; 

and vast areas of U.S. territorial sea (TTS) and exclusive economic zone (EEZ) with rich biodiversity and resources.

 Inspiring and advancing broad understanding of Guam and CNMI’s status as U.S. homeland contributes to 

deterrence against a range of potential threats.

DETAILED DISCUSSION

 Spain ceded Guam to the United States after the Spanish American War in the Treaty of Peace Between the 

United States and The Kingdom of Spain (Treaty of Paris), signed December 10, 1898.

1

 The Guam Organic Act of 1950iv designated Guam as an unincorporated territoryv of the United States;

established executive, legislative, and judicial branches of Government; transferred federal jurisdiction from the 

U.S. Navy to the U.S. Department of the Interior; and granted U.S. citizenship to all persons residing in Guam at 

the time of its enactment and to their children born after April 11, 1899. 

 Persons born in Guam on or after December 24, 1952, acquire U.S. citizenship at birth.

vi

 

1. History & Legal Status of Guam 
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 Unlike CNMI, Guam is considered a Non-Self-Governing Territory by the United Nations – i.e. it is among 17 

territories whose people have not yet attained a full measure of self-government following the colonial period. 

U.N. Member States responsible for 

the administration of such Territories 

are called Administering Powers. The 

United States recognizes its 

obligation as an Administering Power 

under U.N. Charter Article 73(e) to 

promote self-determination for the 

people of Guam.vii

 Although Guam remains a Non-SelfGoverning Territory, federal and local 

laws establishing democratic political 

institutions and strong private sector 

led economies enable locally elected leaders to govern Territorial affairs, thereby mirroring self-governing 

principles. Freely elected leaders establish local priorities, decide resource distribution, and determine ways to

honor their respective cultural identities.

viii

 Guam is listed as part of the definition of the “United States” in section 1011(a)(38) of the Immigration and 

Nationality Act (INA).ix 

 As of the 2020 U.S. Census, Guam’s population is 153,836.x

 CNMI is an unincorporated territory and commonwealth of the United States consisting of 14 of the 15 Mariana 

Islands in the northwest Pacific Ocean (note: Guam, the southernmost Mariana Island, is not part of the CNMI). 

 In 1521 Ferdinand Magellan landed in the Marianas and 

claimed the archipelago for Spain. Following its loss during 

the Spanish–American War of 1898, Spain ceded Guam to the 

United States and sold the remainder of the Marianas (i.e., 

the Northern Marianas) to Germany under the German–

Spanish Treaty of 1899.xi

 Early in World War I, Japan declared war on Germany and 

invaded the Northern Marianas. In 1919, the League of 

Nations awarded all of Germany’s islands in the Pacific 

located north of the equator, including the Northern 

Marianas, under mandate to Japan.xii

 The Trust Territory of the Pacific Islands (TTPI) was 

established in 1947 following Japan’s surrender in World War II. The TTPI included areas which are now CNMI, the 

Republic of the Marshall Islands (RMI), the Federated States of Micronesia (FSM), and the Republic of Palau. The 

United Nations oversaw the TTPI such that each entity could choose its own political arrangement.xiii CNMI 

became an unincorporated U.S. territory via a 1976 resolution titled “The Covenant to Establish a Commonwealth 

of the Northern Mariana Islands in Political Union with the United States of America (The Covenant).”xiv

2. History & Legal Status of CNMI
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 Article III of The Covenant (Citizenship and Nationality), which entered into force in November 1986, declared 

residents of the CNMI to be citizens of the United States.

xv Section 303 of the Covenant also declared all persons 

born in CNMI on or after the effective date of this Section to be citizens of the United States at birth. xvi

 In addition, U.S. federal law (Consolidated Natural Resources Act of 2008) extended most provisions of U.S. 

immigration law to CNMI. In particular, the definition of “United States” in the INA includes CNMI.

xvii

 As of the 2020 U.S. Census, CNMI has a population of 47,329.xviii

 As the most forward U.S. territories in the Pacific, Guam and CNMI are critical to U.S. defense and power 

projection across the region.xix The Guam Defense System is COMUSINDOPACOM’s top homeland defense 

priority, and is central to enabling robust theater logistics.xx

 Guam is DoD’s largest refueling and armament station in the first and second island chains.xxi Sea Ports in Guam 

and CNMI are a three day sail from Taiwan, South Korea, and Japan, and a seven day sail from Hawaii.xxii Airports 

in Guam, Saipain, and Tinian enable direct flights to/from U.S. A&P in the first and second island chains.xxiii

 USINDOPACOM’s stand-up of JTF Micronesia in Guam 

reflects the importance of Guam as a command and 

control node for operations and activities across the 

Guam cluster (Guam , CNI, Wake Island, and Midway 

Island and the Freely Associated States).xxiv 

 Several posture projects in Guam and CNMI require 

historic levels of military construction. Of note, the

United States and the Government of Japan committed 

more than $7 billion for military construction and 

family housing projects on Guam in FY22-FY28. 

 USINDOPACOM’s commitment to homeland defense of 

U.S. territories is reflected in the $1.4 billion 

authorized in NDAA FY’23 for DoD projects in Guam, 

the $1.5 billion for the missile defense in the 

President’s FY’24 Budget, and the establishment of 

Marine Corps Base Camp Blaz, the first new U.S. Marine Corps Base in 72 years. 

 This commitment is also reflected in the $161.8 million expansion to the Tinian Airport in CNMI that will enhance 

turnaround times, maintenance support, and provide an additional divert airfield for DoD Aircraft in the region.xxv

 U.S. A&P are also invested in the region, as evidenced by a Memorandum of Understanding between the United 

States and Singapore for Singapore armed forces to establish a permanent fighter detachment on Guam.xxvi

 According to Singapore’s Ministry of Defense, “the vast training airspace in Guam will allow the Republic of 

Singapore Air Force to conduct realistic training, to hone their capabilities and readiness.”xxvii

 U.S. allies including Japan and Australia also train in Guam. For example, forces from Australia, Japan, and the 

United States established a multinational task force in Guam for exercise Cope North in February 2023.xxviii 

 The U.S. military routinely operates in designated land, air, and sea areas of the Mariana Islands to safely train 

military service members in equipment use, tactics, joint operations, and humanitarian aid missions. These 

training and testing areas are collectively known as the Mariana Islands Range Complex (MIRC).

3. The Significance of Guam and CNMI to Homeland Defense
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 As described by Lt Gen Stephen Sklenka, USINDOPACOM Deputy Commander, “Guam is a place where our 

combat power will aggregate and congregate and from which it will emanate...from there we send a powerful 

strategic message to our allies and our adversaries that the United States has invested in this region.”xxix

 Beyond their significance to military strategy, Guam and CNMI are home to over 200,000 U.S. citizens. 

 The cultures of Guam and CNMI are vibrant, historic, and enduring. Archaeological evidence suggest that 

Austronesian voyagers reached the Marianas 6500 years ago.xxx

 These inhabitants and their descendants became the Chamorro people who formed a strong society and thriving 

culture that continues today.

xxxi

 As U.S. territories, under international law reflected in the U.N. Convention on the Law of the Sea, both Guam and 

CNMI generate U.S. TTS (12-nm sovereign waters) and vast Exclusive Economic Zones (EEZs) (200-nm) with rich 

biodiversity and natural resources subject to U.S. sovereign rights.xxxii

 Tourism, especially from South Korea, Japan, and the United States, accounts for 75% of CNMI’s economy.xxxiii

From 2019-2022 tourism accounted for $3.5 billion of Guam’s total economy (60% of Guam’s revenues).

xxxiv

 USINDOPACOM has an enduring responsibility to ensure the defense of Guam and to CNMI as part of the U.S. 

homeland, and to inform understanding regarding the legal foundation for that defense obligation. 

 The conventional threats that face Guam and CNMI today are numerous. These include threats from intermediate 

and medium range ballistic missiles, such as the DF-26 and DF-21, to H-6K/J/N bombers carrying DH-10 LACM 

cruise missiles and YJ-12 anti-ship missiles.xxxv

 Specifically, both Guam and CNMI are within the 2500-mile firing range of the DF-26 intermediate ballistic missile

dubbed the “Guam Killer” in Chinese media outlets.

xxxvi The DF-26 can fire conventional and nuclear payloads at 

targets across the Marianas.xxxvii

 The People’s Liberation Army (PLA) 

has recently simulated military strikes 

against Guam using H-6K “Badger” 

Bombers.xxxviii

 In 2022, the PLA participated in 

VOSTOK 22, a Russia-led exercise that 

included multiple combined naval 

and strategic bomber patrols. Some 

of those events occurred in the air 

and sea spaces around Japan and 

near Alaska and Guam.xxxix

 PRC propaganda has implied Guam’s

distance from the continental United 

States and proximity to China make it 

a viable target at which the PRC can 

strike if provoked.xl Such propaganda 

denigrates and ignores Guam’s (and 

by extension CNMI’s) status as U.S. homeland indistinguishable as a matter of law from all U.S. territory for 

defense purposes. 

 The Democratic Peoples Republic of Korea (DPRK) has also threatened to strike Guam with its medium to longrange rockets as recently as 2017.xli

4. Conventional Threats to Guam and CNMI 
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 In addition to conventional threats, the U.S. National Security Agency (NSA) and international cybersecurity 

authorities from the Five Eyes (FVEY) partnersxlii issued a combined Cybersecurity Advisory (CSA) spotlighting 

activity associated with a PRC state-sponsored cyber actor known as Volt Typhoon.xliii

 The CSA cites to a report from Microsoft, which says that Volt Typhoon has been active since mid-2021—targeting 

infrastructure in Guam and elsewhere in the U.S. that span sectors such as communications, manufacturing, 

utility, transportation, construction, maritime, government, information technology, and education.

 The authoring agencies of the CSA assessed that Volt typhoon could apply the same techniques against these and 

other sectors worldwide. Volt Typhoon’s techniques reportedly involve infiltrating corporate systems and stealing 

user credentials while avoiding detection for as long as possible. 

 According to the Commander of USINDOPACOM, Admiral Aquilino, the PRC’s “cyber efforts remain focused on 

developing capabilities to enable warfare activities targeting US and partner critical civilian electric, energy, and 

water infrastructure to generate chaos and disrupt military operations.”xliv

 Jen Easterly, the Director of the US Cybersecurity and Infrastructure Security Agency stated that PRC aggression 

against Taiwan is likely to be accompanied by “the explosion of multiple gas pipelines, the pollution of our water 

systems, the hijacking of our telecommunication systems, the crippling of our transportation nodes.” She noted 

that these are activities “all designed to incite chaos and panic across our country and deter our ability to marshal 

military might and citizen will.”xlv The U.S. State Department issued similar warnings that the PRC is capable of 

launching cyber-attacks against critical infrastructure, including oil and gas pipelines and rail systems.xlvi

 A spokesperson for the PRC’s ministry of foreign affairs characterized the CSA as a “collective disinformation 

campaign launched by the US through the Five Eyes to serve its geopolitical agenda.”

xlvii

 Under international law codified in Article 2(4) of the U.N. Charter, states are generally prohibited from using 

force against the territorial integrity or political independence of other states. 

 The U.N. Charter details two relevant exceptions, or circumstances, when a use of force is justified. 

 The first circumstance occurs when the U.N. Security Council determines “the existence of any threat to the

peace, breach of the peace, or act of aggression” and authorizes under Article 42 “such action by air, sea, or land 

forces as may be necessary to maintain or restore international peace and security.”xlviii

 The second circumstance authorizes 

“individual or collective self-defense” under 

Article 51 “if an armed attack occurs against 

a Member.”xlix Customary international law 

also affords states the right to take 

measures in response to imminent attacks.l

 In his volume, Striking First, Doyle 

characterizes self-defense as “[t]he first and 

clearest case of just war. . . The country that 

is attacked and others may join in the 

defensive war in order to repel, and perhaps 

also to punish, an unjust attacker.”li This 

response need not await Security Council 

authorization, though states must apprise the Security Council of the exercise of the inherent right of self6. Legal Authority to Defend Guam and CNMI

5. Cyber Threats to Guam and CNMI 
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defense. The Council may then take “such action as it deems necessary in order to maintain or restore 

international peace and security.”lii

 The United States has consistently recognized that armed attacks on U.S. Territories, just like other U.S. soil, are 

armed attacks on the United States justifying the use for force in self-defense. For example: 

o In May 1846, the Republic of Mexico attacked U.S. Army units in the U.S. territory of Texas. 

o On December 7/8, 1941, the Empire of Japan bombed the U.S. Territories of Hawai’i, Philippines, and 

Guam. 

 In each case the U.S. declared war upon and ultimately defeated the attacker.liii

 U.S. officials have “very clearly stated an attack on Guam [or CNMI] is, in fact, an attack on the U.S. homeland in 

case there had been any misunderstanding about that by the adversary.”liv

 In cyberspace, a state’s inherent right of self-defense may be triggered by cyber operations that amount to an 

armed attack or imminent threat thereof.lv As a matter of policy, the United States has expressed the view that 

when warranted, it will respond to hostile acts in cyberspace as it would to any other threat to the country.lvi

 There is no legal requirement that the response in self-defense to an armed attack in cyberspace take the form of 

a cyber action, as long as the response meets the requirements of necessity and proportionality.lvii

 A state’s right to take necessary and proportionate action in self-defense in response to an armed attack 

(including an armed attack in cyberspace) applies whether the attack is attributed to another state or to a nonstate actor.lviii

 Although cyber operations that do not constitute uses of force would not permit injured states to use force in 

self-defense, those injured states may be justified in taking actions in response that do not constitute a use of 

force,lix such as diplomatic protest, an economic embargo, or other acts of retorsion.lx

 Under international law, states have a right to take countermeasures in response to an internationally wrongful 

act by another state. Countermeasures may not be a use of force and must be necessary and proportionate.

lxi

 Finally, as U.S. territories, Guam and CNMI’s TTS are sovereign U.S. waters, entry and passage through which must

comport with international law.lxii The United States may take steps to prevent entry or passage through TTS that 

is contrary to international law and implementing domestic legislation.

lxiii

 

PROPOSED COUNTER-LAWFARE APPROACH

**This section offers proposed language for incorporation into communication strategies**

 Guam and the CNMI are sovereign U.S. soil and part of the U.S. homeland. They are indistinguishable from the 

fifty states for purposes of defense under international and domestic law. 

 USINDOPACOM's priority mission is to defend the U.S. homeland – that priority mission is based in the inherent 

right of all states to defend their territory and their people from an actual or imminent armed attack. 

 The U.N. Charter’s prohibition on the threat or use of force against the territorial integrity or political 

independence of any state applies with respect to all U.S. territories including Guam and CNMI. 

 As the most forward U.S. territories in the Pacific, Guam and CNMI are critical to U.S. defense and power 

projection. The Guam Defense System is COMUSINDOPACOM’s top homeland defense priority. 

 USINDOPACOM has an enduring obligation to prioritize the defense of Guam and CNMI because of the persistent 

and significant threats they face from potential adversaries. 

 U.S. allies and partners are invested in the Marianas. Singapore armed forces intend to establish a permanent 

fighter detachment on Guam to conduct realistic training and to hone capabilities and readiness. In Feb 2023 

Australian, Japanese, and U.S. forces established a multinational task force in Guam for exercise Cope North. 
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i 48 U.S.C. § 1421 et seq.

ii Id. The Guam Defense System has been described as an architecture extending to the sea and to other islands within the Mariana 

Island chain that provides 360-degree coverage and depth to address threats that originate from air, sea, and land and come from all

directions. See e.g. Lopez, “Time for Guam Missile Defense Build-Up Is Now” https://www.defense.gov/News/NewsStories/Article/Article/2866855/time-for-guam-missile-defense-build-up-is-now/.

iii Id. 

iv 48 U.S.C. § 1421 et seq. 

v Article IV, Section 3 of the US Constitution states that the Congress shall have power to dispose of and make all needful rules and 

regulations respecting the territory or other property belonging to the United States. So-called "unincorporated territory," however, is 

an area over which the Constitution has not been expressly and fully extended by the Congress within the meaning of Article IV, 

Section 3. The recognition of the existence of "unincorporated territory" was determined by the US Supreme Court after the Spanish 

American War. See Definitions of Insular Area Political Organizations, U.S. Department of the Interior. 

vi 8 U.S.C. § 1401(a). Section 301(a) INA provides that a person born in and subject to the jurisdiction of the U.S. shall be a U.S. 

citizen. 8 U.S.C. § 1407(b) INA conferred U.S. citizenship upon anyone born in Guam after April 1899.

vii Department of State, “Charter of the United Nations” Article 73.

viii Ambassador Jeffrey DeLaurentis, “Remarks at the United Nations General Assembly Fourth Committee Joint General Debate on 

Decolonization Items” New York, New York, October 2022.

ix 8 U.S.C. § 1101.

x U.S. Census Bureau, 2020 Census of Guam, https://www.census.gov/newsroom/press-kits/2021/2020-island-area-census-presskit.html. 

xi See Guampedia, Partition of the Marianas, March 2023, https://www.guampedia.com/partition-of-the-marianas/. 

xii See Williams, “Japan’s Mandate in the Pacific” The American Journal of International Law Vol. 27, No. 3. Page 428 (1933).

xiii See Kiste, “Trust Territory of the Pacific Islands” April 2023, https://www.britannica.com/place/Trust-Territory-of-the-PacificIslands. 

xiv 48 U.S.C. §§1801.

xv Id. 

xvi Id.

xvii Public Law 110–229, Consolidated Natural Resources Act of 2008, Title VII.

xviii U.S. Census Bureau, 2020 Census of the Commonwealth of the Northern Marianas Islands.

xix Statement of John C. Aquilino, USINDOPACOM Posture, 18 April 2023.

xx Id. See also Lopez, “Time for Guam Missile Defense Build-up is Now” DOD NEWS, December 2021, https://www.defense.gov/

News/News-Stories/Article/Article/2866855/time-for-guam-missile-defense-build-up-is-now (quoting Lt. Gen. Stephen D. Sklenka, 

USMC).

xxi See Mahshie, “Pacific Refueling” August 2022, https://www.airandspaceforces.com/article/pacific-refueling/.

xxii See Kan and Nisch, “Guam: U.S. Defense Deployments” May 2009, https://safe.menlosecurity.com/doc/docview/

viewer/docNDD58864BE92E4dd5009d3c3ba5d82d2b10fcbc7e764347aa49261b781137ddd29c1622cfb55f. 

xxiii Id.

xxiv See supra note 1. 

xxv Honrada, “U.S. steps up airfield construction on Tinian” June 2022, https://asiatimes.com/2022/06/us-steps-up-airfieldconstruction-on-tinian/.

xxvi This MOU lays out the framework for Singapore’s detachment in Guam, covering the deployment of various airframes and other 

supporting assets for training.

xxvii See “Fact Sheet: Establishment of a Fighter Training Detachment in Guam” December 2019, https://www.mindef.gov.sg/web/

portal/mindef/news-and-events/latest-releases/article-detail/2019/December/07dec19_fs. 

xxviii See Pacific Air Forces, “Australia, Japan, U.S. stand up multinational task force for Cope North 23” January 2023, https://www.

pacaf.af.mil/News/Article-Display/Article/3281228/australia-japan-us-stand-up-multinational-task-force-for-cope-north-23/.

xxix See supra note 21. 

xxx Athens & Ward, “Austronesian Colonisation of the Mariana Islands: The Palaeoenvironmetnal Evidence” Indo-Pacific Prehistory 

Association Bulletin, 21-30, January 2004, Vol. 24 The Taipei Papers, Volume 2.

xxxi Cunningham, Ancient Chamorro Society, 83-96, Bess Press, 1992.

xxxii See U.N. Convention on the Law of the Sea, Arts. 3 & 57, December 1982, 1833 U.N.T.S. 397 (entered into force Nov. 16, 1994); 

see also Proclamation 5030 by the President of the United States of America on the Exclusive Economic Zone of the United States of 

America, 48 Fed. Reg. 50379, March 1983.

 
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xxxiii Commonwealth of Northern Marianas Islands Office of Governor, “Proclamation-Marianas Tourism Month” May 2023, 

https://governor.gov.mp/news/proclamation-marianas-tourism-month-may-2023/.

xxxiv Guam Visitors Bureau, “Over 216K recorded in visitor arrivals for FY 2022” October 2022, https://www.guamvisitorsbureau.

com/over-216k-recorded-visitor-arrivals-fy2022.

xxxv See Zach, “Defending Guam Against the Pacing Threats Of The Pacific” July 2021, https://www.overtdefense.com/2021/07/16/

defending-guam-against-the-pacing-threats-of-the-pacific/.

xxxvi See Wilson, “China’s Expanding Ability to Conduct Conventional Missile Strikes on Guam” August 2016, 

https://cimsec.org/chinas-expanding-ability-conduct-conventional-missile-strikes-guam/; see also Lei, China Daily “PLA deploys 

latest ballistic missile to west brigade” April 2018, www.chinadaily.com.cn/a/201804/18/WS5ad67c0ca3105cdcf6518e29.html.

xxxvii Dangwal, “China’s ‘Guam Killer’ DF-26 Missile ‘Greatest Risk’ For US in Asia-Pacific’ Marine Corps Base Reactivated on 

Island After 68 Years” The EurAsian Times, January 2022, https://eurasiantimes.com/chinas-guam-killer-df-26-missile-greatest-riskfor-us-in-asia-pacific/.

xxxviii See supra note 1. See also Copp, “China has practiced bombing runs targeting Guam, US says” Defense News, October 2017, 

https://www.defensenews.com/flashpoints/2017/10/31/china-has-practiced-bombing-runs-against-guam-us-says/.

xxxix See supra note 1. 

xl Global Times, “Guam is not Pearl Harbor, and China is not Japan” August 2022, https://www.globaltimes.cn/page/202208/

1273806.shtml.

xli BBC, North Korea “Considering missile strike on US Guam base” August 2017, https://www.bbc.com/news/world-asia-40871416.

xlii This advisory from the United States National Security Agency (NSA), the U.S. Cybersecurity and Infrastructure Security Agency 

(CISA), the U.S. Federal Bureau of Investigation (FBI), the Australian Signals Directorate’s Australian Cyber Security Centre

(ACSC), the Communications Security Establishment’s Canadian Centre for Cyber Security (CCCS), the New Zealand National 

Cyber Security Centre (NCSC-NZ), and the United Kingdom National Cyber Security Centre (NCSC-UK) (hereafter referred to as the 

“authoring agencies”).

xliii Cybersecurity Advisory “NSA and Partners Identify China State-Sponsored Cyber Actor Using Built-in Network Tools When 

Targeting U.S. Critical Infrastructure Sectors” May 2023, https://www.nsa.gov/Press-Room/Press-Releases-Statements/Press-ReleaseView/Article/3406058/nsa-and-partners-identify-china-state-sponsored-cyber-actor-using-built-in-netw/).

xliv U.S. Military Posture and National Security Challenges in the Indo-Pacific Region, Full Committee Hearing, April 2023, 

https://armedservices.house.gov/hearings/full-committee-hearing-us-military-posture-and-national-security-challenges-indo-pacific. 

xlv Seldin, VOA News, “US Warns of Massive Chinese Cyberattacks in Taiwan Scenario” https://www.voanews.com/a/us-warns-ofmassive-chinese-cyberattacks-in-taiwan-scenario-/6981396.html. 

xlvi Satter, Siddiqui, and Pearson, “U.S. warns China could hack infrastructure including pipelines, rail systems” May 2023, 

https://www.reuters.com/world/china/china-rejects-claim-it-is-spying-western-critical-infrastructure-2023-05-25/. 

xlvii Ministry of Foreign Affairs of the People’s Republic of China, Foreign Ministry Spokesperson Mao Ning’s Regular Press 

Conference, May 2023, https://www.fmprc.gov.cn/eng/xwfw_665399/s2510_665401/2511_665403/202305/t20230525_

11083609.html. 

xlviii Department of State, “Charter of the United Nations,” Article 42.

xlix Ibid., Article 52.

l Lord Peter Henry Goldsmith, Oral Answers to Questions, April 2004, Hansard 660 House of Commons Debates §§ 370-71 (“It is 

argued by some that the language of Article 51 provides for a right of self-defense only in response to an actual armed attack. 

However, it has been the consistent position of successive United Kingdom Governments over many years that the right of selfdefense under international law includes the right to use force where an armed attack is imminent.”). 

li Doyle, “Striking First: Preemption and Prevention in International Conflict” Princeton University Press, 2008. 

lii Department of State, “Charter of the United Nations,” Article 51. 

liii An Act providing for the Prosecution of the existing War between the United States and the Republic of Mexico, 9 Stat. 9, (1846); 

and Joint Resolution Declaring that a state of war exists between the Imperial Government of Japan and the Government of the people 

of the United States and making provision to prosecute the same, Pub. L. 77-238 (1941). 

liv Gordon, “Missile Defense of Guam is ‘Big Issue,’ DoD Official Says” Air and Space Forces Magazine, November 2022

https://www.airandspaceforces.com/missile-defense-of-guam-is-big-issue-dod-official-says/ (quoting John Plumb, Assistant Secretary 

of Defense for Space Policy).

lv Koh, “International Law in Cyberspace: Remarks as Prepared for Delivery to the USCYBERCOM Inter-Agency Legal Conference”

September 2012, reprinted in 54 Harvard International Law Journal Online, (“Question 4: May a state ever respond to a computer 

network attack by exercising a right of national self-defense? Answer 4: Yes. A state’s national right of self-defense, recognized in 

Article 51 of the UN Charter, may be triggered by computer network activities that amount to an armed attack or imminent threat 

thereof.”); Obama, International Strategy for Cyberspace: Prosperity, Security, and Openness in a Networked World, 10 (May 2011) 
UNCLASSIFIED

9 | P a g e

Prepared by: USINDOPACOM Joint Operational Law Team (J06.pacom@pacom.mil)

Last Updated 10 July 2023 (all prior versions obsolete)

**This TACAID includes legal opinion and analysis that does not necessarily reflect official U.S. government positions.

UNCLASSIFIED

 

(“Right of Self-Defense: Consistent with the United Nations Charter, states have an inherent right to self-defense that may be triggered 

by certain aggressive acts in cyberspace.”).

lvi Obama, International Strategy for Cyberspace: Prosperity, Security, and Openness in a Networked World, 14, May 2011 (“When 

warranted, the United States will respond to hostile acts in cyberspace as we would to any other threat to our country. All states 

possess an inherent right to self-defense, and we recognize that certain hostile acts conducted through cyberspace could compel 

actions under the commitments we have with our military treaty partners. We reserve the right to use all necessary means—

diplomatic, informational, military, and economic—as appropriate and consistent with applicable international law, in order to defend 

our Nation, our allies, our partners, and our interests. In so doing, we will exhaust all options before military force whenever we can; 

will carefully weigh the costs and risks of action against the costs of inaction; and will act in a way that reflects our values and 

strengthens our legitimacy, seeking broad international support whenever possible.”).

lvii Koh, “International Law in Cyberspace: Remarks as Prepared for Delivery to the USCYBERCOM Inter-Agency Legal 

Conference” September 2012, reprinted in 54 Harvard International Law Journal Online, 4, December 2012, (“There is no legal 

requirement that the response to a cyber armed attack take the form of a cyber action, as long as the response meets the requirements 

of necessity and proportionality.”).

lviii United States Submission to the U.N. Group of Governmental Experts on Developments in the Field of Information and 

Telecommunications in the Context of International Security 2012-2013, 2 (“As the United States noted in its 2010 submission to the 

GGE, the following established principles would apply in the context of an armed attack, whether it originated through cyberspace or 

not: The right of self-defense against an imminent or actual armed attack applies whether the attacker is a State actor or a non-State 

actor.”). 

lix Department of Defense, Office of the General Counsel, An Assessment of International Legal Issues in Information Operations (2nd 

ed., Nov. 1999), reprinted in 76 U.S. Naval War College International Law Studies, 459, 482 (2002). (“There is also a general 

recognition of the right of a nation whose rights under international law have been violated to take countermeasures against the 

offending state, in circumstances where neither the provocation nor the response involves the use of armed force. For example, an 

arbitral tribunal in 1978 ruled that the United States was entitled to suspend French commercial air flights into Los Angeles after the 

French had suspended U.S. commercial air flights into Paris. Discussions of the doctrine of countermeasures generally distinguish 

between countermeasures that would otherwise be violations of treaty obligations or of general principles of international law (in 

effect, reprisals not involving the use of armed force) and retorsions – actions that may be unfriendly or even damaging, but which do 

not violate any international legal obligation. The use of countermeasures is subject to the same requirements of necessity and 

proportionality as apply to self-defense.”).

lx See DoD Law of War Manual 16.3.3.3.

lxi See supra note 60. (“There is also a general recognition of the right of a nation whose rights under international law have been 

violated to take countermeasures against the offending state, in circumstances where neither the provocation nor the response involves 

the use of armed force. For example, an arbitral tribunal in 1978 ruled that the United States was entitled to suspend French 

commercial air flights into Los Angeles after the French had suspended U.S. commercial air flights into Paris. Discussions of the 

doctrine of countermeasures generally distinguish between countermeasures that would otherwise be violations of treaty obligations or 

of general principles of international law (in effect, reprisals not involving the use of armed force) and retorsions – actions that may be 

unfriendly or even damaging, but which do not violate any international legal obligation. The use of countermeasures is subject to the 

same requirements of necessity and proportionality as apply to self-defense.”).

lxii See UNCLOS Article 45. For example, states enjoy a right of innocent passage through a coastal state’s TTS.

lxiii See, e.g., The Commander’s Handbook on the Law of Naval Operations, NWP 1-14M/MCTP 11-10B/COMDTPUB P5800.7A 

(2022 ed.), ¶2.5.2.1 (“[A] coastal State make take affirmative action in and over its territorial sea to prevent passage that is not 

innocent, including, where necessary, the use of force.”).