On 28 September 2026, Argentina's President instructed the Foreign Ministry and government legal teams to institute arbitral proceedings against the United Kingdom under Annex VII of the United Nations Convention on the Law of the Sea, seeking to halt hydrocarbon exploitation in the 'North Malvinas Basin' through the Sea Lion project.

Argentina gave the UK two weeks to adopt measures stopping Sea Lion and said it will seek provisional measures from the International Tribunal for the Law of the Sea (ITLOS) to preserve its claimed sovereign rights over the continental shelf. It is, as far as observers can determine, the first time Argentina has publicly announced an intention to file UNCLOS proceedings over the Falkland Islands/Islas Malvinas dispute.

Why an Annex VII tribunal?

Both States are UNCLOS parties but have chosen different procedures under Article 287: Argentina selected ITLOS, while the UK chose the International Court of Justice. By default, the case will therefore go to an Annex VII arbitral tribunal unless the parties agree otherwise. Pending its constitution, Argentina may request ITLOS to prescribe provisional measures under Article 290(5) — but only if the future tribunal would prima facie have jurisdiction.

What blocks Argentina's claims?

The compulsory settlement system under Article 288(1) covers only disputes "concerning the interpretation or application" of UNCLOS. Territorial sovereignty is not regulated by the Convention. In its 320 articles and nine annexes, no provision determines which State holds sovereign title over land territory. UNCLOS repeatedly refers to the 'coastal State' without defining one.

As Robert Beckman has observed: "territorial sovereignty disputes are governed by rules of customary international law on the acquisition and loss of territory, not by UNCLOS … UNCLOS was never intended to resolve issues of sovereignty."

The precedent is consistent. Annex VII tribunals have declined jurisdiction whenever claims required deciding unresolved sovereignty over land:

• Chagos Marine Protected Area (Mauritius v. UK, 2015): the majority held the dispute was really about land sovereignty.
• Coastal State Rights (Ukraine v. Russia, 2020): no jurisdiction to the extent claims required ruling on Crimea's status.
• South China Sea (Philippines v. China, 2015): jurisdiction upheld only insofar as claims could be decided without ruling on sovereignty.

Unlike Mauritius in the 2021 Mauritius/Maldives ITLOS Special Chamber case, Argentina cannot point to an authoritative ICJ finding in its favour to render the sovereignty question moot. If ITLOS finds no prima facie jurisdiction, it will decline to prescribe measures halting Sea Lion.

Could a status quo argument work?

Argentina's announcement invokes UNGA Resolutions 2065 (XX) (1965) and 31/49 (1976), suggesting it may claim the UK must not unilaterally modify the situation pending resolution of the sovereignty dispute. This strategy echoes the self-restraint obligations in Articles 74(3) and 83(3) for undelimited maritime areas. Yet those provisions presuppose overlapping entitlements generated by coastal sovereignty. If Argentina denies UK sovereignty over the Islands, no overlapping entitlements — and hence no delimitation dispute — exist.

Claims grounded in UNGA resolutions or general international law, including Article 2(3) of the UN Charter, may not qualify as disputes about UNCLOS's interpretation or application. ITLOS and Annex VII tribunals rejected human rights claims per se on this basis in M/V Norstar (2019) and Arctic Sunrise (2015).

Are environmental claims Argentina's best route?

Environmental claims may offer a way around the sovereignty obstacle. In Coastal State Rights and South China Sea, tribunals admitted claims concerning protection and preservation of the marine environment — obligations that can be agnostic as to which State is sovereign. An Argentine federal judge has reportedly ordered a halt to Sea Lion on the basis that it threatens marine ecosystems and wildlife. To obtain provisional measures, however, Argentina must evidence "something more specific than general considerations of environmental harm."

What does this mean for practitioners?

For now, Sea Lion proceeds under licences granted by the Falkland Islands Government, with the UK's stated "full support". The UK insists the sovereignty matter is closed, citing the Islanders' wish to remain a British Overseas Territory. Argentina's Foreign Ministry has reiterated readiness to resume bilateral negotiations, reviving ideas such as Marcelo Kohen's 2018 proposal for negotiated sovereignty transfer with Island autonomy, or a joint special regime covering resource access, environmental cooperation and demilitarisation, along the lines of the 1995 Joint Declaration that Argentina terminated in 2007, citing "British unilateral acts uninterruptedly performed since 1995 in spite of Argentina's repeated protests."

The next stage of this longstanding dispute remains to be seen.