To Advise or Not to Advise? – Advisory Opinion Jurisdiction of ITLOS as a Full Court

von JOHANNES IPSEN und MAREN SOLMECKE

In the latest advisory opinion of the International Tribunal for the Law of the Sea (ITLOS) as a full court the question, whether it enjoys advisory opinion jurisdiction as full court was – after a thorough examination in ITLOS´ first advisory opinion with a full bench and despite remaining objections – not comprehensively discussed again. Compared to the International Court of Justice’s (ICJ) advisory opinion jurisdiction the legal basis for ITLOS as a full court has convincingly been described as e.g., “fragile”, even though it is arguably possible to identify certain acceptance by States.

Introduction

In May 2024 the International Tribunal for the Law of the Sea (ITLOS) rendered an advisory opinion as a on the request by the COSIS. It has received wide attention, since it addresses climate change in the context of the Law of the Sea. ITLOS opined that ocean warming and acidification caused by anthropogenic greenhouse gas emissions constitute marine pollution within the meaning of Art. 1 para 1 (4) UNCLOS. Further, the advisory opinion addressed the question which specific obligations apply to the State parties of UNCLOS considering the ongoing climate crisis. However, whether ITLOS as full court is entitled to render advisory opinions per se was – after a thorough examination in the very first advisory opinion given by ITLOS as a full court, but despite remaining objections – not comprehensively discussed again. The legal basis for ITLOS to render advisory opinions as a full court has convincingly – especially compared to the advisory opinion jurisdiction of the Seabed Dispute Chamber – been described as “fragile” by Yoshifumi Tanaka. Nevertheless, it is arguably possible to identify acceptance by States, particularly in light of the proceedings of the recent advisory opinion and the adoption of the BBNJ-Agreement.

UNCLOS and Advisory Opinion Proceedings

UNCLOS contains only one provision expressly dealing with advisory opinions. Art. 191 UNCLOS empowers the Seabed Dispute Chamber (a special chamber of ITLOS) to render advisory opinions at the request of the Assembly or the Council – two organs of the International Seabed Authority. Regarding the scope, the Seabed Dispute Chamber may only give advisory opinions within the scope of activities of these organs. This limits it to questions concerning the maritime zone the Area. In contrast, neither UNCLOS nor the ITLOS-Statute expressly provide a legal basis for ITLOS as a full court to render advisory opinions. In the 2015 advisory opinion by ITLOS as a full court, ITLOS spent 33 paragraphs justifying its jurisdiction. In the view of the tribunal, the decisive provision is Art. 21 ITLOS-Statute. It reads:

“The jurisdiction of the Tribunal comprises all disputes and all applications submitted to it in accordance with this Convention and all matters specifically provided for in any other agreement which confers jurisdiction on the Tribunal.” (emphasis added)

According to ITLOS the term “all matters” means something different from and more than “disputes” and, thus, includes advisory opinions. Art. 21 ITLOS-Statute constitutes together with the required “other agreement” the substantive legal basis for the advisory jurisdiction. Considering Art. 138 ITLOS-Rules, which expressly addresses the advisory jurisdiction of ITLOS as a full court, ITLOS – rightly – ruled that it (only) furnishes the prerequisites for advisory opinion proceedings and does not provide a legal base for the jurisdiction.

In light of the (non-legally binding) important power of advisory opinions, the reasoning by ITLOS is, however, not fully convincing. Basing the advisory jurisdiction on the referred part of Art. 21 ITLOS-Statute becomes frail considering other international treaties which contain provisions expressly stipulating an advisory competence in the treaty or in the agreed Statutes of the respective tribunals. In this regard, the International Court of Justice (ICJ) serves as a good reference. It can rely on Art. 96 UN-Charta and Chapter IV ICJ-Statute, which expressly confer the advisory jurisdiction to the ICJ and at the same time foresee limitations to the proceedings. Like the UN-Charta and the ICJ-Statute, UNCLOS itself expressly acknowledges the advisory opinion jurisdiction for – but only for – the Seabed Dispute Chamber. When it comes to the jurisdiction of ITLOS as a full court, ITLOS must utilize Art. 21 ITLOS-Statute and a respective other agreement as basis for its jurisdiction. This seems like a somewhat unorganic way, particularly regarding the fact that advisory opinion proceedings are, like the international dispute settlement, based on the principle of consent, due to the sovereignty of the participating States. Whether an interpretation of a legal basis as extensive as ITLOS’ still covers the necessary requirements of this principle is at least debatable.

Acceptance by States?

With these inconsistencies in mind, one may argue that an increased acceptance by States can be observed for two reasons: Firstly, by comparing the proceedings of the 2015 advisory opinion those of the 2024 advisory opinion it becomes apparent that the number of States formulating their hesitancy or their objection towards the jurisdiction of ITLOS as a full court decreased (around half of the States participating in the 2015 compared to roughly a quarter of States participating in 2024). Secondly, for the sake of contextual interpretation, the adoption of the BBNJ-Agreement – even though not in force yet – arguably speaks in favour of the acceptance of States of ITLOS advisory opinion jurisdiction as a full court. Its Art. 47 para 7 reads:

“The Conference of the Parties may decide to request the [ITLOS] to give an advisory opinion (…).“ (emphasis added)

Since the BBNJ-Agreement has 105 signatories that are mostly also members of UNCLOS at the time of writing, it may reflect States’ consent to the general mechanism of advisory proceedings in front of ITLOS as a full court. Thus, it can be argued that the advisory jurisdiction for ITLOS as a full court has been accepted by States.

Concluding Remarks and Outlook

The Post is entitled “To Advise or Not to Advise?”. In light of the above, we conclude that the legal basis for ITLOS to render advisory opinions as a full court is questionable. However, against the backdrop of the advisory opinion in 2024 and the adoption of the BBNJ-Agreement, arguably the jurisdiction has been accepted by the State community. Therefore, the answer is “To Advise”. Nevertheless, we would like to highlight the critically broad scope of ITLOS’ advisory competence and the sparse regulations for submitting such requests. Momentarily two States may conclude an international agreement to request advisory opinions by ITLOS as a full court, constituting a risk of misuse of advisory opinion proceedings. Even though the BBNJ-Agreement acknowledges the advisory jurisdiction for ITLOS as a full court, it foresees significant limitations for the access to and the scope of advisory opinions. Whether this (should) reflect(s) on ITLOS’ competence to give advisory opinions requires further research. To continue in style, one may ask “To Advise! But How Far?”

This blog post is a shortened version of a research paper that was presented and discussed during the UN Research Colloquium “Global Transformations: The International System at a Crossroads?” that took place on 25^th and 26^th October 2024 in Lüneburg.

Zitiervorschlag: Ipsen, Johannes und Maren Solmecke, To Advise or Not to Advise? – Advisory Opinion Jurisdiction of ITLOS as a Full Court, JuWissBlog Nr. 13/2025 v. 06.02.2025, https://www.juwiss.de/13-2025/

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