Legal ambiguity in the Strait of Hormuz due to U.S. and Iranian non-party status to UNCLOS increases risks of conflict

The disagreement between Iran and the United States over the application of the international law of the sea in the Strait of Hormuz increases the chance of war. Perhaps not surprisingly, the antagonists disagree on the source as well as the content of the law that applies in the Strait. With the January 8, 2013 accession by Timor-Leste, there are now 165 States party to UNCLOS. The treaty recognizes that coastal States may claim a twelve nautical mile territorial sea, measured from the low water mark running along the shore.8 Ships of all nations enjoy the right of innocent passage through the territorial sea.⁹ On the other hand, coastal States have broad and durable security interests in the territorial sea, and may prescribe and enforce laws that condition or preclude altogether the surface transit of foreign warships.

When overlapping territorial seas connect one area of the high seas or exclusive economic zone (EEZ) to another area of the high seas or EEZ, this also constitutes a strait used for international navigation under the terms set forth in UNCLOS.¹⁰ States are entitled to exercise the right of transit passage through such straits used for international navigation. The regime of transit passage affords more rights to users of the strait than innocent passage. In most circumstances, innocent passage can be sus- pended by the coastal State; transit passage cannot be suspended. Transit passage also allows submerged transit and overflight of aircraft through the strait.¹¹ Only surface transits are permitted for ships engaged in inno- cent passage. In the absence of acceptance of UNCLOS, however, the United States and Iran cannot use these clear rules as a guide and therefore must revert to legacy treaties, such as the 1958 Convention on the Territo- rial Sea and Contiguous Zone (Territorial Sea Convention),¹² as well as customary international law, to determine their respective rights and duties in the strait.