The law governing both carrying and using a marine radio station aboard boats and yachts is not really complex. The difficulty is in knowing which of the various U.S. and International organizations govern and in which circumstance.
Generally speaking, there are only 2 aspects of the law that are of interest to the average boater:
There are four primary organizations that contribute to these laws:
The IMO regulates the outfitting and operation of most vessels engaged on international voyages, except warships.
NTIA regulates all use of radio onboard any federal government vessel, including military vessels. NTIA rules do not apply outside the federal government.
The FCC regulates all sales, marketing, and, use of radios in the U.S., including those onboard any recreational, commercial, state and local government, and foreign vessel in U.S. territorial waters.
The USCG regulates carriage of radio on most commercial vessels, foreign vessels in U.S. waters, survival craft, and vessels subject to the Bridge-to-Bridge Act (generally all vessels over 20m length) and operating in a Vessel Traffic Service (VTS) area.
In general terms this means that we can ignore NTIA; and the IMO only comes into play if we are on an international voyage or communicating with a foreign radio station. The last two, the USCG and the FCC are the largest influencing factors on U.S. boaters.
Simply put, the FCC regulates the use of radios in the U.S. and the USCG regulates which vessels are required to carry them.