The United Nations Convention on the Law of the Sea (UNCLOS) is heralded as a constitution for the oceans, and as part of this, provides for a compulsory dispute settlement procedure entailing binding decisions. However, case law and academic commentary have highlighted significant issues in definitively identifying other agreements that could preclude these compulsory procedures – a concept permitted by the Convention in certain circumstances. This paper begins to explore this challenge by contending that the type of agreement plays a significant role in whether or not it could be determined to be an ‘exclusionary agreement’. In doing so, the article conducts a systematic interpretation of Articles 281 and 282 UNCLOS, underpinned by the application of relevant provisions in the Vienna Convention on the Law of Treaties. This provides a conclusive basis as to whether the status of an agreement as an ‘ad hoc agreement’ (specific; adopted for the dispute) or an ‘existing agreement’ (general; adopted prior to the dispute) holds any significance in the context of these articles.