Strait of Hormuz - Unfortunately in the Strait of Hormuz and the waters to the west of it, shipping lanes run close to and in some areas through Iranian territorial waters. Under international maritime law the Iranians are entitled to monitor this traffic but the traffic, including warships, is entitled to unimpeded transit. As the US and Iran view each other with great mistrust, the potential for conflict is high.
Two things complicate the matter further. The first is that the USA has not ratified (formally agreed to abide by) the relevant legislation on international maritime law: the United Nations Convention on the Law of the Sea. The second is that, according to UNCLOS, if there are islands lying off a nation’s coast then the 12 miles extend from the outermost island.
The area of sea around the Strait of Hormuz contains several islands, for many of which the ownership is claimed by both Iran and the United Arab Emirates, a pro-western country. Whoever owns the islands will own the territorial waters around them, according to international maritime law as it is usually interpreted.