May the United States Unilaterally Conduct or Regulate Activities in the Area According to International Law?
By Eduardo Cavalcanti de Mello Filho
Published on 4 April 2025
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On 27 March 2025, The Metals Company (TMC), a Canadian company, announced that its US subsidiary will apply for exploitation permits under the US 1980 Deep Seabed Hard Mineral Resources Act (DSHMRA) (here). This move is controversial, since it seeks a unilateral alternative to the system established by the 1982 UN Convention on the Law of the Sea (UNCLOS), as implemented by the 1994 Agreement on UNCLOS Part XI, which regulates activities in the international seabed Area (the “Area”) through the International Seabed Authority (ISA).
Under UNCLOS Article 136, the Area and its resources are governed by the Common Heritage of (Hu)Mankind (CHM) principle, which is concretised in Part XI. However, TMC argues that, because the US is not an UNCLOS State Party, it enjoys the high seas freedom of deep seabed mining. TMC’s involvement with the ISA and deep seabed mining is well-known, but its purported backing by the Trump Administration and members of Congress (here) raises a pressing question: May the US unilaterally conduct or regulate activities in the Area?
In this piece, I argue that it may not. First, because the CHM principle has become customary international law (CIL). Second, the argument that the US has been a “persistent objector” to this rule since its formation is flawed, for the US objection has not been “maintained persistently,” and, in any case, the CHM principle is arguably a peremptory norm of international law, i.e., it admits of no “persistent objection.”
Customary International Law, Part XI and the CHM Principle
There is little doubt today that CIL reflects Part XI, as a concrete expression of the CHM principle, to the extent possible (e.g., CIL does not cover procedural rules pertaining to the functioning of a specific organization) (here). Even if one defends that only certain elements of the CHM principle have become customary, it is certain that one of these is the rule precluding non-States Parties from unilaterally conducting activities in the Area, codified in UNCLOS Article 137(3) (e.g., here). The CHM principle, as detailed in UNCLOS, is largely useless without this rule.
Pushing for the universality of the CHM principle is UNCLOS itself, as it can be assumed that its 170 States Parties generally consider Part XI to be of general application, including to non-States Parties. By its very subject-matter (the regulation of a global common), Part XI has been conceptualised as an “objective regime,” which, under an orthodox understanding of international law, reaches non-States Parties through CIL.
The US understood this when it voted for the 1970 Declaration of Principles Governing the Area. Affirming the CHM principle, US Representative Stevenson explained that the meaning of the “common heritage [would] be elaborated in the internationally agreed regime to be established (here).” According to one of the greatest law of the sea scholars in US-American history, Jon Van Dyke, two of the principles governing this elaboration process were the following: “a ‘generally accepted’ law of the sea treaty can establish a seabed regime even for nonparties” and “even if no treaty is signed, claims of exclusive rights to seabed resources will be prohibited (here).”
Historical responses to US sporadic defiance reinforce this point. For example, the 1984 Provisional Understanding Regarding Deep Seabed Mining, negotiated by the US with Belgium, France, Germany, Italy, Japan, the Netherlands, and the UK, was designed to coordinate unilateral mining activities as a high seas freedom. However, the UNCLOS Preparatory Commission rebuked any regime that was “incompatible with [UNCLOS] and [stated that] its related resolutions shall not be recognized (here);” the G77 framed it as “wholly illegal (here);” Tommy Koh, the President of the UNCLOS conference, suggested requesting the International Court of Justice to declare it illegal in an advisory opinion (here).
Since then, joining 163 States. all other parties to the Provisional Understanding have become UNCLOS States Parties, with some even sponsoring companies under ISA contracts (here). The US remains the only outlier, and universal adherence is not a requirement for the formation of CIL rules. In any case, although the US is a “specially affected State” due to its technological prowess, its opposition to Part XI has been inconsistent, as discussed below.
The US Objection: Lacking Persistence
Assuming the “persistent objector” doctrine is valid in general international law (as the UN International Law Commission has done), the US does not meet its requirements. The Reagan administration (1981–1989) initially opposed Part XI, defending deep seabed mining as a high seas freedom (here), but subsequent US actions have been inconsistent, i.e. there has been no “persistence.”
TMC cites the DSHMRA as evidence of long-standing US opposition, but this overlooks key facts. First, the issuance of four DSHMRA exploration licenses is immaterial as objection to Part XI. The 1984 licenses have not included at-sea activities, and two of them have been surrendered in 1997 and 1999 (here). Lockheed Martin, which holds the two remaining ones, in requesting their extensions, has simply sought to “maintain its [US law-based] interests and rights under these exploration licenses (here).”
In a 2012 letter to the US Senate supporting UNCLOS ratification, its chairman clarified that “investments needed to establish an ocean-based resource development business must be predicated upon clear legal rights established and protected under the treaty-based framework of the LOS Convention (here).” Extending its licences aim to preserve a pathway for ISA-based sponsorship for activities in the licence-designated areas.
Second, the DSHMRA was intended as a temporary measure “pending adoption of an acceptable international regime (here).” The 1994 Agreement addressed US concerns, leading President Clinton to sign it (here), with the George W. Bush and Obama administrations also supporting accession to UNCLOS (here, here). Crucially, the US has never “unsigned” the 1994 Agreement or declared it would not join it, despite recommendations from the Reagan-aligned Heritage Foundation (here).
To the contrary, recognising that the 1994 Agreement “satisfies the criteria under DSHMRA,” the US National Oceanic and Atmospheric Administration (NOAA) has understood that the 1980 Act “provides authority to implement likely United States obligations under the Agreement (here).” While it is unclear how far DSHMRA can go in “provisionally applying” the 1994 Agreement parallelly to the ISA, the US Congressional Research Service recognised that “without the United States being a party to UNCLOS, U.S. citizens issued licenses or permits by NOAA would have no legal recourse to protect their claim to explore and/or recover seabed minerals in ANBJ (here).”
As if this were not enough “inconsistence,” the US also signed the 2023 Agreement on Biodiversity Beyond National Jurisdiction, whose Article 7(b) reads “to achieve the objectives of the Agreement, Parties shall be guided by […] [the CHM principle] which is set out in [UNCLOS].” These commitments not only undermine any claim to persistent objection but also create obligations under general international law. As a signatory, the US is bound under CIL (codified in Article 18 of the 1969 Vienna Convention on the Law of Treaties (VCLT)) to “refrain from acts which would defeat the object and purpose of a treaty.”
More broadly, the US objection to Part XI pales compared with other well-documented “persistent objections” responding to UNCLOS developments. Examples include Colombia’s stance on the regime of islands, Iran’s objection to transit passage in straits, and Turkey’s rejection of the 12-nautical-mile territorial sea limit. By contrast, the US record on Part XI is riddled with contradictions, way beyond the very few ones mentioned here.
The CHM Principle is a peremptory norm of international law
Even if the US had maintained a consistent objection, this would not be valid against peremptory norms of international law (jus cogens). VCLT Article 53 defines them as a “norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted.” Based on what was seen in the section on CIL, it is not bold to assert that the “international community of States as a whole”—except for, maybe, the contradictory US—understands that the CHM principle admits of no derogation and, as a corollary, of no “persistent objection.” This is true at least for States Parties to UNCLOS, whose Article 311(6) forbid them from being “party to any agreement in derogation” of the CHM principle.
State reactions to past and present US attempts to bypass Part XI reinforce this point. The 1980s saw widespread opposition to the US position, and similar responses emerged when TMC announced its plans in during the ISA Council session in March 2025. Governments from all regions condemned the move, viewing it not just as a violation of CIL but as an attempt to override a fundamental pillar of the contemporary ocean legal order. The US delegation at the ISA, with observer status, remained silent (here).
In my view, the CHM principle is to the Area what the right of peoples to self-determination is to national jurisdiction—a core principle that admits of no exception, derogation, or objection. Therefore, all States have the obligation to not recognise the legality of activities conducted in serious breach of this principle (here), such as the issuing of mining permits for the TMC. That UNCLOS States Parties have a similar duty of non-recognition under Article 137(3) further corroborates with the view that the CHM principle is jus cogens.
Finally, in Judge Ammoun’s words in his Namibia opinion, this duty implies that “States and their subjects must refrain from acquiring any of the production of these exploitations, in order not to incur civil responsibility by being involved either as receivers or as purchasers, with notice, of assets not belonging to the vendor (here).” For they belong to humankind.
Eduardo Cavalcanti de Mello Filho is a Research Associate (Ocean Law and Policy) at the Centre for International Law, National University of Singapore.