Sea Lion Goes to Hamburg? Provisional Measures Pending the Constitution of an Annex VII Tribunal

[Lesther Antonio Ortega Lemus is a Guatemalan Lawyer and the Director of LexOceana, an Ocean Affairs and International Law practice based in The Hague. He has served as Guatemala’s representative to several UK- and Netherlands-based international organisations (IMO, ISO, PCA, ICC, OPCW, et al.) and as Deputy Head of Mission and Acting Head of Mission at Guatemala’s Embassies in the UK and the Netherlands.]

Recent Developments

On 28 September 2026, Argentina announced that President Milei had instructed its Foreign Ministry and governmental legal teams to institute Annex VII proceedings under the United Nations Convention on the Law of the Sea (UNCLOS) regarding offshore hydrocarbon developments around the Malvinas/Falkland Islands, singling out the Sea Lion project. It demanded that the UK take measures within two weeks to prevent the commencement or continuation of activities directed toward resource exploitation, or otherwise it would seek provisional measures from the International Tribunal for the Law of the Sea (ITLOS). 

The UK’s response asserted its compliance with international law, especially UNCLOS, without denying the existence of a dispute or the prospective Annex VII tribunal’s jurisdiction. In its 1 October statement, Argentina said it has placed its case before “independent arbitrators” and characterised unilateral exploration and exploitation of non-renewable resources in the disputed area as a modification contrary to the General Assembly’s Resolution 31/49. 

Under UNCLOS Article 290(5), pending constitution of an Annex VII arbitral tribunal, ITLOS may prescribe provisional measures if it considers that the future tribunal would prima facie have jurisdiction and that the situation’s urgency requires them. Unlike the ICJ’s exercise of its power under Article 41 of its Statute, ITLOS acts in support of arbitration before another tribunal which, once constituted, may modify, revoke or affirm those measures.

The immediate question is whether Argentina can obtain interim protection regarding resource activities while leaving sovereignty over the islands unresolved.

The Procedural Gateway Under Article 290(5)

Article 290(5) permits recourse to ITLOS where the parties have not agreed, within two weeks of notification of a request for provisional measures, on a court or tribunal to prescribe them. Whether Argentina’s announced deadline corresponds to that procedural period depends on the underlying diplomatic communication. Its latest statement does not reproduce the request or clarify its terms.

ITLOS has prescribed measures pending the constitution of Annex VII Tribunals in 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), and San Padre Pio (2019). Argentina successfully invoked the incidental procedure in ARA Libertad, while the UK appeared as respondent in MOX Plant.

Article 287(5) provides for Annex VII arbitration where the parties have not accepted the same dispute-settlement mechanism, unless they otherwise agree. Argentina and the UK have selected different procedures, so Annex VII applies by default.

Argentina’s statement indicates that it regards the arbitration as instituted. The notification and statement of claim should identify the dispute submitted, its claimed jurisdictional basis and the relief it seeks. Any preceding diplomatic exchanges would also require examination against the obligation to exchange views regarding settlement by negotiation or other peaceful means, as prescribed by Article 283.

These procedural requirements lead to the first substantive question: whether the prospective tribunal would prima facie have jurisdiction over Argentina’s claims. 

Prima Facie Jurisdiction and the Sovereignty Question

Annex VII case law offers an approach to jurisdiction where UNCLOS claims coexist with contested territorial sovereignty. The decisions considered below addressed jurisdiction beyond the provisional measures stage, yet their reasoning informs the inquiry under Article 290(5): characterising the dispute, determining whether adjudication requires a sovereignty ruling, and identifying claims capable of examination independently of such a ruling. 

In the Chagos MPA Arbitration, the Tribunal’s majority examined the “relative weight” of the sovereignty and Convention issues, and subsequently declined jurisdiction over Mauritius’ first two submissions. It left open, without deciding, whether a minor issue of territorial sovereignty could be ancillary to a Convention dispute (Award, paras 211-221, 229-230). The Tribunal nevertheless asserted jurisdiction over specified aspects of the fourth submission under Articles 288 (1) and 297 (1) (c)  (para. 323). The UK’s undertakings supplied rights whose existence did not depend on Mauritius first establishing territorial sovereignty (para. 448). The case therefore illustrates the importance of identifying rights that can be adjudicated independently of territorial title. 

In the South China Sea Arbitration, the Tribunal examined whether resolving the Philippines’ submissions required an express or implicit sovereignty determination, or whether their actual objective was to advance its position in the sovereignty dispute. It found neither condition present and considered that the submissions could be approached on the premise that China’s sovereignty assertions were correct (Jurisdiction Award, paras 152-154). 

In Coastal State Rights, the tribunal concluded that sovereignty over Crimea was a prerequisite to deciding a number of Ukraine’s claims. It excluded claims whose adjudication necessarily required an express or implicit sovereignty determination and directed Ukraine to revise its Memorial. The proceedings continued although the tribunal deferred a separate jurisdictional objection concerning the Sea of Azov and the Kerch Strait to the merits stage (Preliminary Objections Award, paras 193-198, 492 (a)-(d)).

These decisions support a claim-specific inquiry. Argentina may thus formulate submissions the determination of which leaves territorial title unresolved; independently justiciable claims may also survive the exclusion of sovereignty-dependent submissions. The decisive consideration is the substance of the claims and premises necessary to decide them, rather than simply the omission of sovereignty from the prayer for relief. 

Independence from territorial sovereignty does not, by itself, settle jurisdiction. Each claim must fall within Article 288 and remain outside any applicable limitations or exceptions under Articles 297 and 298. Both States have Article 298 declarations. The UK’s declaration of 31 December 2020 excludes the category specified in Article 298 (1)(a) concerning maritime delimitation and historic bays or titles. Its relevance will depend on the tribunal’s characterisation of the claims submitted.

Under Article 290(5), ITLOS must assess if the provisions invoked prima facie afford a basis for arbitral jurisdiction, albeit not making a definite determination (San Padre Pio, Order, para. 45). The awards demonstrate that an underlying sovereignty dispute need not exclude every UNCLOS-based claim. Their significance in the dispute at hand turns on identifying Convention-based obligations governing resource activities whose application does not depend on first establishing Argentine sovereignty.  

Restraint over Resource Exploitation: Plausibility and the Link to the Measures Requested

Argentina will also need to establish that the rights it seeks to protect are plausible and that a link exists between those rights and the measures requested (Ghana/Côte d’Ivoire, Provisional Measures Order, paras 58, 62–63). Its most recent communiqué invokes General Assembly Resolution 31/49, which calls upon the parties to refrain from decisions introducing unilateral modifications while the recommended process continues. The question is how that position relates to Convention obligations capable of supporting interim protection.

Resolution III annexed to the Final Act of the Third United Nations Conference on the Law of the Sea merits attention in this context. It addresses the exercise of maritime rights where sovereignty over a qualifying territory remains disputed, envisaging consultations and practical provisional arrangements pending settlement. Its language echoes Article 83(3), reflecting a consistent approach in the Convention and Resolution III: cooperation through provisional arrangements and restraint against conduct that would jeopardise or hamper an eventual settlement. The resolution’s relevance to the particular Convention obligations invoked would depend on Argentina’s submissions.

The distinction between entitlement to resources and the rights governing their exploitation pending settlement remains significant. Argentina might seek protection of the latter without requesting a determination of entitlement to the resources themselves. Whether such rights permit adjudication independently of territorial sovereignty would depend on their legal basis and content.

The measures requested must correspond to the rights asserted. A request to suspend drilling or exploitation would require an explanation of how the anticipated activities threaten those rights and why restraint is necessary to preserve them. The nature of the rights would therefore guide the form and scope of relief.

That connection leads to the question of timing: why protection is required before the Annex VII Tribunal can act. 

Sea Lion: Urgency and Irreparable Prejudice

Article 290(5) directs attention to the period before the Annex VII Tribunal is constituted and able to act. A real and imminent risk of irreparable prejudice during that interval can justify interim protection. For Argentina, Sea Lion’s anticipated progression provides the factual setting for establishing that risk (San Padre Pio, Order, para. 111).

Drilling and other offshore works may precede extraction and affect the rights asserted before the arbitral tribunal can act. The relevant timetable is therefore not confined to the commencement of production. The supplied evidence would therefore concern both the timing of the activities and the point at which they would impair the effective exercise of the particular asserted right. Scheduled operations, project approvals and any implementation arrangement would help establish that connection.

The consequences of offshore operations also deserve attention. In Ghana/Côte d’Ivoire, ITLOS’ Special Chamber distinguished compensable revenue losses from physical changes to the seabed and subsoil that financial compensation could not fully remedy (Order, paras 88–91). That case concerned delimitation and measures under Article 290(1), but the distinction remains instructive. Its relevance here would depend on connecting the anticipated physical changes to prejudice to the particular rights Argentina seeks to preserve.

Commercial considerations may inform the design of relief. In the same case, the Special Chamber considered the financial and environmental consequences of suspending ongoing operations, while requiring that no new drilling take place (paras 99-102). Early measures may limit the disruption associated with later suspension, although that consideration does not in itself replace the requirements of urgency and irreparable prejudice.

Environmental protection presents a distinct possibility if supported by Argentina’s claim and the evidence. Article 290 (1), applicable through paragraph 5, expressly authorises measures to prevent serious harm to the marine environment alongside measures preserving the parties’ respective rights. Article 41 of the ICJ Statute contains no equivalent express environmental limb. This ground remains subject to the applicable jurisdictional and urgency requirements, nevertheless. 

In MOX Plant, while declining to suspend the plant’s operation, ITLOS prescribed cooperation, information exchange and consideration of measures to prevent pollution. Its reasoning concerned cooperation in protecting the marine environment under Part XII (Order, paras 81–84, 89(1)). The decision illustrates how measures can be adapted to the obligations and risks established before the Tribunal. 

Argentina’s application could bring together the operational timetable, the consequences of impending activities and the rights requiring preservation. Those elements would inform both the need for interim protection and the measures appropriate during the period before the Annex VII Tribunal can act.

Conclusions

An underlying sovereignty dispute need not foreclose interim protection of distinct UNCLOS-based rights. Annex VII case law supports examining the claims individually, including whether they can be decided without determining territorial title. For ITLOS, the question would be whether the prospective tribunal has prima facie jurisdiction over the claims for which protection is sought. 

Sea Lion’s progression gives that question practical significance. If impending activities threaten irreparable prejudice to plausible rights before the arbitral tribunal can act, Article 290(5) provides an avenue for protection. Whether that avenue leads to interim measures will turn on the relationship between the rights asserted, the anticipated activities and the relief sought, within the jurisdictional limits examined above.