Defining the Boundaries of Extended Continental Shelves: Analysis of the ICJ Judgment in Nicaragua v. Colombia (2023)

Written by Jomart Joldoshev, LL.M. as part of the International Courts Reporter series

The International Court of Justice (ICJ) recently made an important ruling in the case of Nicaragua v. Colombia, which has set a significant precedent in international maritime law. This case focused on two main issues: countries’ rights to extend their continental shelves beyond 200 nautical miles and the protection of Exclusive Economic Zones (EEZs) within that limit. The ICJ’s decision strongly supports the idea that EEZ boundaries, once established, should remain secure and not be disrupted by claims of extended continental shelves from neighboring countries.

The dispute between Nicaragua and Colombia began with Nicaragua’s 2013 request to extend its continental shelf beyond the usual 200-nautical-mile limit based on the natural prolongation of its land territory under the sea. This claim, however, overlapped with Colombia’s already established 200-mile EEZ. The ICJ’s task was to decide if Nicaragua’s extended claim could legally encroach on Colombia’s EEZ. This question has broad implications for how countries approach maritime boundaries in the future.

In its analysis, the ICJ referred to two main criteria under customary international law that allow countries to claim continental shelf rights: the distance criterion and the natural prolongation criterion. The distance criterion automatically gives countries rights to continental shelves within 200 nautical miles of their coastlines. The natural prolongation criterion applies when a country’s continental shelf naturally extends beyond the 200-mile limit. Despite recognizing both criteria, the Court emphasized that a country’s EEZ within the 200-mile limit precedes any overlapping extended continental shelf claims. This priority is established under customary international law. It is also reflected in the United Nations Convention on the Law of the Sea (UNCLOS), a widely accepted legal guide, although Colombia has not signed it. The Court thus reinforced that once a country’s EEZ is defined, it cannot be overridden by neighboring countries’ claims to extend continental shelves unless there is an explicit agreement between them.

The ICJ examined how countries act in similar cases to support this position and looked at widely accepted legal opinions (opinio juris). The Court found that most countries avoid claiming continental shelves that would overlap with another country’s EEZ when submitting applications to the Commission on the Limits of the Continental Shelf (CLCS). This common practice demonstrates a broad agreement that EEZ boundaries should remain exclusive and not be subject to overlapping claims.

The ICJ distinguished the Nicaragua v. Colombia case from earlier cases, particularly the Bay of Bengal disputes (Bangladesh v. Myanmar and Bangladesh v. India). In those cases, maritime boundaries were adjusted between neighboring countries with overlapping claims, creating “grey areas” where an extended continental shelf partially overlapped with another country’s EEZ. However, the Court clarified that these cases dealt with unique geographical situations that required adjustments and did not create a general rule allowing one country’s extended continental shelf to infringe on another’s established EEZ. Instead, the Bay of Bengal cases were examples of necessary adjustments for fair boundary setting between neighbors, distinct from Nicaragua v. Colombia, where an extended continental shelf claim overlapped an already established EEZ boundary.

The Nicaragua v. Colombia ruling has critical implications for international maritime law and future boundary disputes, offering several key takeaways. First, the ICJ’s decision affirms that EEZ boundaries within the 200-nautical-mile limit are paramount and cannot be overridden by claims to an extended continental shelf. Second, it highlights the importance of clearly defining maritime boundaries, ensuring that EEZ rights remain protected once set unless countries mutually agree otherwise. Third, in cases of overlapping claims, the ICJ encourages countries to seek peaceful and cooperative resolutions through diplomatic talks and agreements rather than through unilateral actions.

By reinforcing the exclusivity of EEZ rights, the ICJ’s ruling enhances the stability and predictability of international maritime law. This decision not only aligns with the principles outlined in UNCLOS but also strengthens the established practices of countries in submitting maritime claims, encouraging diplomatic discussions over conflicting claims.

The ICJ’s ruling in Nicaragua v. Colombia helps create a more orderly maritime framework where established EEZ boundaries are respected and not subject to overlapping claims. The decision affirms that extended continental shelf claims must respect existing EEZ boundaries, a principle likely to guide other countries dealing with similar overlapping claims. Its impact extends beyond Nicaragua and Colombia, providing a reference point for other countries managing complex maritime boundary disputes. By prioritizing stable and clear EEZ boundaries, the ICJ has set a lasting standard that values predictability, respect for sovereignty, and the peaceful negotiation of boundary issues in international waters.