What Is The Jones Act?

I just  returned from an 8 day cruise with Ron and my mom.  What a wonderful time we had!  Great food, service, wonderful entertainment and interesting lecturers, made this trip all I expected, and more.  The cruise sailed from Los Angeles to San Francisco, then down to Puerto Vallarta, and back again to Los Angeles.  One of the cruise stops was San Diego, and many passengers wanted to disembark there.  They couldn't.  Why?  Because of the Jones Act.  We didn't know what the Jones Act was, but here is Wikepedia's information on the Jones Act:


The Merchant Marine Act of 1920 is a United States federal statute that provides for the promotion and maintenance of the American merchant marine.^[1] Among other purposes, the law regulates maritime commerce in U.S. waters and between U.S. ports. Section 27 of the Merchant Marine Act is known as the Jones Act and deals with cabotage (coastwise trade) and requires that all goods transported by water between U.S. ports be carried on U.S.-flag ships, constructed in the United States, owned by U.S. citizens, and crewed by U.S. citizens and U.S. permanent residents.^[2] The act was introduced by Senator Wesley Jones. The law also defines certain seaman's rights.
Laws similar to the Jones Act date to the early days of the nation. In the First Congress, on September 1, 1789, Congress enacted Chapter XI, "An Act for Registering and Clearing Vessels, Regulating the Coasting Trade, and for other purposes", which limited domestic trades to American ships meeting certain requirements.^[3] Such laws served the same purpose as – and were loosely based on – England's Navigation Acts, which were finally repealed in 1849.

I'm not sure what any of this has to do with passengers on a cruise ship, but I guess it does.  In any event, we got off in Puerto Vallerta (foreign port), but others had to stay on another 6 days and get off in Los Angeles.