With the response to Hurricane Maria in Puerto Rico lagging badly behind that seen in the U.S. Virgin Islands, and after growing public calls for action, the U.S. finally waived the Jones Act for a time.  This will allow a wider range of ships to transit directly between ports in the U.S. and the Caribbean island territory.

The Jones Act is an example of "cabotage law," meaning regulation of trade between domestic ports.  Laws like it exist in most countries and the intent originally was to protect fleets of merchant marine ships and personnel from competition from other countries.  The fear was that if other countries could push domestic ship building out of business and reduce the number of native sailors.  In the event of a war such a weakness could have been disastrous for most countries dependent on trade over water.  The law forces trade (passenger travel or goods and services) traveling from one U.S. port to another must be built in the U.S., crewed by Americans, and owned by Americans.  The Passenger Vessel Services Act of 1920 is very similar and applies to passenger vessels specifically.  The PVSA however states that no ship failing any of the three mandates in the Jones Act can pick passengers up in one U.S. port, then debark them at a different U.S. port without visiting a second country first.
In this case the Jones Act prevents fleets of ships that fail any of the three mandates to travel directly from American ports to Puerto Rico.  This had the effect of crippling shipments of needed supplies and materials needed to aid hurricane recover efforts.
Within the cruise industry and beyond there is strong sentiment to update and change the Jones Act and the PVSA to reflect modern times.  Such would allow for radical growth in cruises that travel entire itineraries of U.S. and Canadian ports, boost tourism in said ports and certainly create new jobs.  However the Jones Act and PVSA have staggeringly well funded, determined and organized union and business interests who have successfully defended the laws for nearly a hundred years.  Some think the hurricanes might finally lead to some changes but there seems little momentum given the current political climate in the U.S.