[2] Many economists and other experts have argued for its repeal,[4] while military and U.S. Department of Commerce officials have spoken in favor of the law on protectionist grounds.

He said the act was "an earnest effort to lay the foundation of a policy that will build up and maintain an adequate American merchant marine in competition with the shipping of the world.

In 1988, Congress specified that waterborne transport of valueless material, such as dredge spoil or municipal solid waste, requires the use of a Jones Act-qualified vessel.

Cabotage is "trade or navigation in coastal waters, or the exclusive right of a country to operate the air traffic within its territory".

[15] The cabotage provisions relating to the Jones Act restrict the carriage of goods or passengers between U.S. ports to U.S.-built and flagged vessels.

[16] Generally, the Jones Act prohibits any foreign-built, foreign-owned, or foreign-flagged vessel from engaging in coastwise trade within the United States.

§ 30104, which provides: Any sailor who shall suffer personal injury in the course of his employment may, at his election, maintain an action for damages at law, with the right to trial by jury, and in such action all statutes of the United States modifying or extending the common-law right or remedy in cases of personal injury to railway employees shall apply....The law allows U.S. seamen to bring actions against ship owners based on claims of unseaworthiness or negligence, rights not afforded by common international maritime law.

Workers who spend less than 30 percent of their time in the service of a vessel on navigable waters are presumed not to be seaman under the Jones Act.

The Court ruled that any worker who spends more than 30 percent of their time in the service of a vessel on navigable waters qualifies as a seaman under the act.

[21] The Jones Act prevents foreign-flagged ships from carrying cargo between the contiguous U.S. and certain noncontiguous parts of the U.S., such as Puerto Rico, Hawaii, Alaska, and Guam.

In June 2012, the Federal Reserve Bank of New York indicated that the Jones Act may hinder economic development in Puerto Rico, although a Government Accountability Office report found the effect of repealing or loosening is uncertain, with possible tradeoffs.

The report also addresses what would happen "under a full exemption from the Act, the rules and requirements that would apply to all carriers would need to be determined."

It continues, "While proponents of this change expect increased competition and greater availability of vessels to suit shippers' needs, it is also possible that the reliability and other beneficial aspects of the current service could be affected."

Because the Jones Act requires that all transport between U.S. ports be carried on U.S.-built ships, its proponents claim that it supports the domestic U.S. shipbuilding industry.

Proponents say that by keeping the industrial base working, the Jones Act ensures that the Navy and Marine Corps can spin up shipbuilding without relying on other nations.

A 2011 Government Accountability Office (GAO) study found there are about 5 million maritime crew entries into the U.S. each year, and "the overwhelming majority of seafarers entering U.S. ports are aliens."

In addition, the act is seen as a vital factor in maintaining a viable workforce of trained merchant mariners for commerce and national emergencies.

Supporters also argue that allowing foreign-flagged ships to engage in commerce in domestic American sea lanes would undermine U.S. wage, tax, safety, and environmental standards.

[43] According to the Lexington Institute, the Jones Act is also vital to national security and plays a role in safeguarding America's borders.

[44][45] The Lexington Institute wrote in a 2016 study that the Jones Act plays a role in strengthening U.S. border security and helping to prevent international terrorism.

[47] Critics contend that the Act results in higher costs for moving cargo between U.S. ports, particularly for Americans living in Hawaii, Alaska, Guam, and Puerto Rico.

[54] Open America's Waters Act to repeal restrictions on coastwise trade was again submitted, as S. Bill 1646 by Senator Lee on May 13 2021, during the 117th United States Congress.

[59][60] Requests for waivers of the Act and its provisions are reviewed by the Department of Homeland Security on a case-by-case basis, and can only be granted based on interest of national defense.

In the wake of Hurricane Katrina, Homeland Security Secretary Michael Chertoff temporarily waived the coastwise laws for foreign vessels carrying oil and natural gas from September 1 to 19, 2005.

[61][62] In order to conduct an emergency shipment of gasoline from Dutch Harbor, Alaska, to Nome in January 2012, Secretary of Homeland Security Janet Napolitano granted a waiver to the Russian ice class marine tanker Renda.

[68][69] Requests for waivers of certain provisions of the act are reviewed by the United States Maritime Administration (MARAD) on a case-by-case basis.

[71] Pressure exerted by 21 agriculture groups, including the American Farm Bureau Federation, failed to secure a Jones Act waiver following Hurricane Katrina in the Gulf of Mexico.