The US has never ratified the 1982 Law of the Sea convention. Iran changed the law in 1993. So we have a set of confusing claims on the Straits of Hormuz and the rights of transit.
http://www.globalsecurity.org/military/ops/arabian-gauntlet.htm"On May 2, 1993, the Government of Iran completed legislative action on an "Act on the Marine Areas of the Islamic Republic of Iran in the Persian Gulf and the Oman Sea." The legislation provides a reasonably comprehensive set of maritime claims to a territorial sea, contiguous zone, exclusive economic zone (EEZ), and continental shelf, and Iran's jurisdictional claims within those areas. Many of these claims do not comport with the requirements of international law as reflected in the 1982 United Nations Convention on the Law of the Sea (LOS Convention). Warships and certain other ships are, contrary to international law, required to receive prior approval to engage in innocent passage.
Iran's requirement for prior approval is not recognized by the US. The LOS Convention does not permit a coastal State to require a foreign vessel to seek the prior authorization of, or notification to, the coastal State as a condition of conducting innocent passage through its territorial sea. Warships representing a wide variety of nations pass through Iran's territorial sea in innocent passage without objection from Iran, despite Iran's requirement that prior authorization be obtained for each transit. These examples of State practice, shared in by many nations and fully consistent with international law, appear to outweigh Iran's claims to restrict freedom of navigation. The US protested this stated requirement in 1983 and 1987, conducted operational assertions in 1989 and 1992 of prior permission requirement, and conducted regular transits of the Strait of Hormuz starting in 1983.
As of 2007 the United States remained a non-signatory of the 1982 United Nations Law of the Sea Convention (USCLOS), yet strongly supports the navigational causes contained therein. The U.S. Freedom of Navigation program has ensured that excessive coastal state claims over the world’s oceans and airspace are repeatedly challenged. By diplomatic protests and operational assertions, the United States has insisted upon adherence by the nations of the world to the international law of the sea, as reflected in the UN Law of the Sea Convention."