Admiralty or Maritime Law is a body of law governing navigation and shipping. Admiralty law is under the specific domain of federal law, created through Article III of the Constitution. Maritime Law governs not only U.S. tidal waters, but any waters within the United States used for navigation. Because Maritime Law is governed exclusively by the federal branch, states have no jurisdiction to legislate or govern maritime matters.
Under Admiralty law, a ship’s flag determines what country has jurisdiction. Thus, an American ship flying an American flag off the coast of Africa, is still governed by American maritime law; similarly, a Russian ship on the coast of California would be governed by Russian maritime law. Nevertheless, an American court could still exercise jurisdiction over the Russian ship – the court could decide whether to apply Russian maritime law or refuse to exercise jurisdiction.
In general international maritime law is consistent among all countries.