If you are a fan of the NPR Podcast "Planet Money," you may recall an episode from 2014 entitled "Mr. Jones' Act," wherein David Kestenbaum & Zoe Chace analyzed The Merchant Marine Act of 1920, commonly known as the Jones Act, after Senator Wesley Jones of Washington.  The law is an extremely broad statute, and is codified in various portions of Title 46 of the United States Code.

The episode is linked below.

https://www.npr.org/sections/money/2017/09/27/553990861/episode-524-mr-jones-act

I highly recommend listening to it.

The Jones Act governs the rights of maritime workers, creates causes of action in tort, and imposes restrictions on the vessels that can travel from one U.S. port to another.  The last set of restrictions are sometimes called Cabotage Laws, or in the United States, the Coastwise Trading Act.  See 46 U.S.C. 55101-55122.  The First Congress under our current U.S. Constitution passed  similar restrictions on vessel movement in the Tariff of 1789.

The original reason for the focus on Mr. Jones' Act by NPR was the winter storms of 2013-2014.  As seen in this NPR article from February 2014, Jones Act restrictions prevented a Marshall Islands-flagged vessel from moving 40,000 tons of salt between Maine and New Jersey.

https://www.npr.org/sections/money/2014/02/28/283451010/how-an-old-law-caused-a-modern-day-salt-shortage

More recently, in 2017, the Trump Administration temporarily waived the Jones Act to allow for foreign flagged vessels to travel from one U.S. port to Puerto Rico to provide relief from Hurricane Maria.  However, the waiver expired and was not renewed.

If you have any specific questions about the Jones Act, or comments about its continued necessity/viability, please feel free to leave them below.