By Marcus Bennett | Global Law Wire

On 28 September 2026, Argentina announced that President Milei had instructed his government to launch Annex VII proceedings against the United Kingdom under UNCLOS. The dispute singles out the Sea Lion offshore hydrocarbon project around the Malvinas/Falkland Islands.

Argentina's Foreign Ministry gave the UK two weeks to halt exploration and exploitation work in the disputed waters. If London refused, Argentina said it would ask the International Tribunal for the Law of the Sea (ITLOS) for provisional measures.

In a 1 October statement, Argentina said it had placed the case before "independent arbitrators." The statement also characterized unilateral activity in non-renewable resources as a modification contrary to General Assembly Resolution 31/49. The UK replied by asserting compliance with international law, especially UNCLOS, without denying the existence of a dispute or the prospective Annex VII tribunal's jurisdiction.

The stakes are high. Sea Lion sits in waters both countries have claimed for decades.

What does Article 290(5) of UNCLOS permit?

Article 290(5) lets ITLOS prescribe provisional measures pending the constitution of an Annex VII arbitral tribunal. The tribunal must believe the future body would prima facie have jurisdiction. The situation must also require urgent action.

Unlike the ICJ under Article 41 of its Statute, ITLOS acts in support of arbitration before another tribunal. Once constituted, that tribunal may modify, revoke or affirm the measures.

ITLOS has used this authority nine times since 1999. The cases are:

• Southern Bluefin Tuna (1999)
• MOX Plant (2001)
• Land Reclamation (2003)
• ARA Libertad (2012)
• Arctic Sunrise (2013)
• Enrica Lexie (2015)
• Detention of Three Ukrainian Naval Vessels (2019)
• San Padre Pio (2019)

Argentina won interim relief in ARA Libertad. The UK appeared as respondent in MOX Plant.

Can ITLOS act when sovereignty itself is disputed?

Annex VII tribunals have answered this question three times. Each decision examined claims individually rather than treating sovereignty as a blanket bar.

In the Chagos Marine Protected Area Arbitration, the majority weighed sovereignty against Convention issues and declined jurisdiction over Mauritius's first two submissions. It left open whether a minor sovereignty question could be ancillary to a UNCLOS dispute (Award, paras 211-221, 229-230). The tribunal then asserted jurisdiction over parts of the fourth submission (para. 323).

In the South China Sea Arbitration, the tribunal found that none of the Philippines's submissions required a sovereignty ruling (Jurisdiction Award, paras 152-154). In Coastal State Rights, the tribunal excluded claims needing a sovereignty determination and directed Ukraine to revise its Memorial (Preliminary Objections Award, paras 193-198, 492(a)-(d)).

Both states have filed Article 298 declarations. The UK's declaration, dated 31 December 2020, excludes maritime delimitation and historic bays or titles under Article 298(1)(a). How that exclusion applies will turn on how Argentina frames its claims.

Does Sea Lion's timeline create urgency?

Article 290(5) covers the window before the Annex VII tribunal can act. Real and imminent risk of irreparable prejudice in that interval can justify interim relief (San Padre Pio, Order, para. 111).

Drilling often comes before extraction. The relevant timetable stretches from project approvals through implementation, well before production begins, according to the analysis. Argentina would need to show both the timing and the impairment to the specific right it asserts.

In Ghana/Côte d'Ivoire, ITLOS's Special Chamber separated compensable revenue losses from physical changes that money could not fix (Order, paras 88-91). The same chamber weighed financial and environmental costs of suspending operations against requiring that no new drilling occur (paras 99-102).

Article 290(1), applied through paragraph 5, also lets ITLOS order measures to prevent serious harm to the marine environment. The ICJ Statute contains no equivalent express environmental limb. In MOX Plant, ITLOS declined to suspend the plant but ordered cooperation, information exchange and pollution prevention under UNCLOS Part XII (Order, paras 81-84, 89(1)).

What is Argentina likely to ask for?

Resolution III, annexed to the Final Act of the Third United Nations Conference on the Law of the Sea, addresses maritime rights where sovereignty remains disputed. It calls for consultations and provisional arrangements. Its language echoes Article 83(3) and reflects a shared principle: restraint against conduct that would hamper eventual settlement.

Argentina may seek protection of rights governing exploitation without asking for a ruling on resource entitlement. A request to suspend drilling would need to explain how the planned work threatens those rights.

The link between the activities, the rights, and the relief requested is decisive. Without it, ITLOS cannot grant interim protection, even if Sea Lion's timetable appears to favor Argentina's urgency claim.