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The United States Has Declared the Boundaries of Its Extended Continental Shelf: What Comes Next?

On December 19th, 2023 the United States declared the boundaries of its extended continental shelf,[1] which represents the outermost maritime zone over which it exercises sovereignty.  This declaration was significant because it represented a major step in definitively establishing the United States’ maritime boundaries in accordance with international law. However, while the declaration does much to clarify the reaches of U.S. maritime sovereignty, it also raises a number of questions about the status of these boundaries under international maritime law.

In 1982, international efforts to codify the customary international law of the sea culminated in the creation of the Law of the Sea Convention (“UNCLOS”)[2] which established a scheme of maritime “zones” over which a state exercises varying degrees of sovereignty. The outermost of these zones is the “extended continental shelf” (“ECS”), and it represents the continuation of a state’s territorial landmass underneath the surface of the ocean.[3] Within the ECS, states have exclusive rights to exploit the resources of the sea floor.[4] UNCLOS sets out detailed technical criteria for how to determine the boundaries of a state’s ECS.[5] It also established the Commission on the Limits of the Continental Shelf (“CLCS”), a treaty organization comprised of scientific experts whose purpose is to make recommendations on submissions from coastal states on the boundaries of their ECS. UNCLOS provides that “the limits established by a coastal state on the basis of these recommendations shall be final and binding.”[6]

The United States’ ECS announcement declared the previously ambiguous boundaries of its own continental shelf including areas in the Atlantic Ocean, the Pacific Ocean, the Gulf of Mexico, and the Bering Sea.[7] However, the largest and most significant U.S. ECS zone lies in the Arctic Sea off the northern coast of Alaska. The Arctic Sea potentially contains significant natural resources including minerals and rare earth elements,[8] and therefore is strategically valuable for the five states which assert ECS claims in the area: Canada, Denmark, Norway, Russia, and the United States.[9]

Notably, the United States is not a signatory to UNCLOS. Therefore, it is unclear exactly to what extent its declaration of its ECS zone binds other states. The United States made clear in its announcement that it considers the provisions of UNCLOS to represent customary international law.[10] In 2012, the International Court of Justice confirmed that states have sovereignty over their ECS under customary international law, however it was silent as to what extent UNCLOS’s technical provisions for determining the boundaries of a state’s ECS also have the status of customary international law.[11] Several scholars have argued that these technical standards have obtained the status of international law due to widespread state practice and opinion juris.[12] In its announcement, the United States stated that it determined the boundaries of its ECS in accordance with the UNCLOS technical standards.[13] Kevin Baumert argues that because these provisions of UNCLOS have likely ascended to the status of customary international law, the ECS boundaries established by the United States in accordance with these provisions are likely binding under customary international law.[14]

One consequence of the United States’ unilateral declaration as a non-signatory to UNCLOS, however, is that its boundaries were not determined “based on the recommendations” of the CLCS and therefore are not “final and binding” as a matter of treaty law under UNCLOS.[15] One open question is whether, as a non-signatory party, the United States may make a submission to the CLCS for their review. The United States indicated its willingness to do so, stating that it would be consistent with the CLCS’s mission to provide recommendations to “coastal states.”[16] Kevin Baumert has argued that the term “coastal state” can be distinguished from the term “State Parties” used elsewhere in the treaty and therefore this term supports the conclusion that the CLCS may consider submissions from non-parties.[17] Some Russian media outlets, however, criticized the United States’ announcement and argued that it could not unilaterally establish its ECS boundaries outside the procedures of the CLCS.[18]

A final consideration following the United States’ announcement is whether it should become a party to UNCLOS. Several administrations have been in favor of joining.[19] Congress last held a hearing on the matter in 2012, but no action has since been taken.[20] While it remains to be seen whether the United States will join UNCLOS, the unexplored resources of the ECS, and consequently the international law of the sea governing these resources, will continue to be highly relevant in the years to come.

Matt Salavitch is a staff member of Fordham International Law Journal Volume XLVII.

[1]  Announcement of U.S. Extended Continental Shelf Outer Limits, U.S. Dep’t of State (Dec. 19, 2023), https://www.state.gov/announcement-of-u-s-extended-continental-shelf-outer-limits/.

[2] Kevin A. Baumert, The Outer Limits of the Continental Shelf Under Customary International Law, 111 Am. J. Int’l L. 827, 829 (2017).

[3] U.N. Convention on the Law of the Sea, art. 76, Dec. 10, 1982, 1833 U.N.T.S. 397 [hereinafter UNCLOS].

[4] Evan T. Bloom, Jeremy Greenwood, Securing U.S. Territorial Rights In The Arctic: New Actions To Protect America’s Continental Shelf 2 (2022), https://www.wilsoncenter.org/sites/default/files/media/uploads/documents/Bloom%20-%20Securing%20US%20Territorial%20Rights%20in%20the%20Arctic.pdf. While states exercise exclusive jurisdiction over the resources of the seabed, the water column above the ECS remains international waters. Id.

[5] UNCLOS, Art. 76(2)-(7).

[6] UNCLOS, Art. 76(8).

[7] The Outer Limits of the Extended Continental Shelf of the United States of America, United States Dep’t of State 7 (2023), https://www.state.gov/wp-content/uploads/2023/12/ECS_Executive_Summary.pdf [hereinafter U.S. ECS Announcement].

[8] James Kraska, Strategic Implication of the US Extended Continental Shelf, Wilson Center (Dec. 19, 2023),

https://www.wilsoncenter.org/article/strategic-implication-us-extended-continental-shelf.

[9] Bloom et. al., supra note 4.

[10] U.S. ECS Announcement at 7.

[11] North Sea Continental Shelf (Ger. v. Den.), 1969 ICJ Rep. 3, ¶ 63, at 39–40 (Feb. 20).

[12] J.N. Moore, Customary International Law After the Convention, in The Developing Order Of The Oceans 41, 43 (Robert B. Krueger & Stefan A. Riesenfeld eds.,1985); Thomas A. Clingan Jr., The Law of the Sea in Prospective: Problems of States Not Parties to the Law of the Sea Treaty, 30 Germany. Y. B. Int’l L. 101, 111 (1987).

[13] U.S. ECS Announcement at 6.

[14] Baumert, supra note 2 at 862. As customary international law, the reaction of other states are relevant in determining whether these boundaries are acceptable as a matter of customary international law. Id.

[15] UNCLOS, Art. 76(8).

[16] U.S. ECS Announcement at 6.

[17] Baumert, supra note 2 at 867. It should be noted, however, that even if the United States were to make a submission to the CLCS, it would likely be years before it would get considered, given that the CLCS reviews submissions in the order received and there are currently submissions from over fifty countries outstanding. Submission to the Commission on the Limits of the Continental Shelf, United Nations, Division for Ocean Affairs and the Law of the Sea (Oct. 30, 2023), https://www.un.org/Depts/los/clcs_new/commission_submissions.htm.

[18] See Chekunkov: The United States, having announced the expansion of the shelf in the Arctic, neglects the international format, TACC (Dec. 25, 2023), https://tass.ru/politika/19625359; Kosachev: The Americans have surpassed themselves by ignoring the interests of even their allies in the Arctic, RG.RU (Dec. 25, 2023),  https://rg.ru/2023/12/25/kosachev-amerikancy-prevzoshli-samih-sebia-proignorirovav-interesy-dazhe-svoih-soiuznikov-v-arktike.html. The United States delimited its ECS boundaries in the Arctic Sea in accordance with a 1990 treaty between itself and Russia that established a maritime boundary between the two nations. Agreement Between the United States of America and The Union of Soviet Socialist Republics on the Maritime Boundary, Russ.-U.S., opened for signature June 1, 1990, S. TREATY DOC. NO. 101–22 (1990) (entered into force provisionally June 15, 1990).

[19] Law of the Sea Convention, Nat’l Oceanic and Atmospheric Admin., U.S. Dep’t of Comm. (Jan. 5, 2023), https://www.noaa.gov/law-of-sea-convention.

[20] Law of the Sea Convention, U.S. Dep’t of State, https://www.state.gov/law-of-the-sea-convention/.

This is a student blog post and in no way represents the views of the Fordham International Law Journal.