The Extended Continental Shelf in Nicaragua v Colombia : Identifying a Customary Rule Based on CLCS Submissions?

In Nicaragua v Colombia, the International Court of Justice (ICJ) identified a rule in customary international law which prohibited a state from asserting an extended continental shelf (ECS) that encroaches on maritime areas within 200 nautical miles (NM) of another state. While the ICJ reached this conclusion based on the practice of states parties' submissions to the Commission on the Limits of the Continental Shelf (CLCS), in which a vast majority of states parties had refrained from asserting an ECS that extends within the 200 M line of another state, the ICJ's approach appears flawed. On an inductive examination of the existing CLCS submissions, it is evident that while a number of states have exercised restraint when asserting their ECS, the CLCS submissions do not indicate sufficiently widespread and uniform state practice nor opinio juris supporting the identification of a customary rule as asserted by the ICJ.