Q: How are sales regulated on cruise ships? do the onboard shops/stores follow the laws of the ship's flag state?

A: In summary, onboard shops and stores on cruise ships typically follow the laws of the ship's flag state, but U.S. laws apply when the ship is within U.S. territorial waters or under specific international agreements.

Sales on cruise ships are primarily regulated by the laws of the ship's flag state. This principle is well-established in international maritime law, which dictates that the internal affairs of a ship, including commercial transactions, are governed by the law of the country whose flag the ship. This rule is known as the "law of the flag" and is recognized by the U.S. Supreme Court and other courts as a fundamental aspect of maritime law.

However, when a ship is within the territorial waters of the United States, U.S. law applies. This includes regulations related to sales and other commercial activities conducted on board. For instance, U.S. law would govern the sale of alcohol on a cruise ship while it is in U.S. territorial waters, but once the ship leaves these waters, the law of the flag state would generally take precedence.

Additionally, specific agreements between the United States and the flag state of a vessel can also influence the application of U.S. jurisdiction. For example, under certain conditions, foreign vessels calling at U.S. ports may be subject to U.S. jurisdiction if there is an agreement recognizing such jurisdiction. This means that while the law of the flag state generally governs, there can be exceptions based on international agreements and specific circumstances.