Its goals were twofold. First, it was intended to support a national maritime industry that could mobilize for war or a national emergency. Second, it was intended to protect American control over local waterborne commerce.

Those opposed to the act have long included officials and allies of Hawaii, Alaska and Puerto Rico, who say that the law increases shipping costs for goods from the mainland, which are then passed on to consumers. Its supporters include pro-defense groups and members of the domestic shipping industry whose interests it protects.

Some criticized calls for the suspension, arguing that it was not clear how much good it would do and that delivery delays were being caused by problems moving goods inland, not importing them.

Why did Puerto Ricans want a waiver?

In a Monday letter to the head of the Department of Homeland Security, eight members of Congress asked for a temporary waiver of the act, arguing that lifting it would expand access to food, medicine, clothing, building supplies and oil needed for power plants.

“Puerto Rico can’t borrow funds and they are required to use American shipping only, which is the most expensive in the world. In their hour of need, Washington can help by suspending the Jones Act,” one of the letter’s signatories, Representative Luis V. Gutiérrez, Democrat of Illinois, said in a statement at the time.

A day later, Senator John McCain, Republican of Arizona, voiced his support for the effort.

“It is unacceptable to force the people of Puerto Rico to pay at least twice as much for food, clean drinking water, supplies and infrastructure due to Jones Act requirements as they work to recover from this disaster,” he said on Tuesday.

Mr. McCain, long an advocate for repealing the law, most recently advanced legislation to do so in July. He renewed his call for repeal on Thursday after the waiver was announced.