Trump administration officials countered that the surge of migrants at the border was a growing catastrophe and that something had to be done. “This rule is a lawful exercise of authority provided by Congress to restrict eligibility for asylum,” Attorney General William P. Barr said. “The United States is a generous country but is being completely overwhelmed by the burdens associated with apprehending and processing hundreds of thousands of aliens along the southern border.”

For decades, the United States’ willingness to serve as a place of safety for those trying to escape violence and brutality has been an expression — at times unfulfilled — of the country’s values around the globe.

The asylum system, long a part of American law, was meant to give immigrants a legal opportunity to live in the United States only when they could demonstrate that they would face persecution, torture or death if they returned to their home countries.

But from the moment he came into office, Mr. Trump has called the country’s asylum laws little more than permissive loopholes. “The asylum rules and laws are so bad that our Border Patrol people, who are so incredible, aren’t allowed to do their jobs,” the president said recently.

Mr. Trump argues that migrants are gaming the system by falsely claiming asylum and then skipping out on their court hearings. In fact, the government’s own statistics show that most asylum seekers show up for their court hearings, especially if they are represented by a lawyer.

However, the waiting period to be heard in court can be years because of a backlog of more than 900,000 immigration cases. By the time immigrants show up for their hearings, they have often put down roots with children, jobs and mortgages.

Few asylum claims are granted — the Trump administration says only 20 percent are, and immigration advocates say some 40 percent are — but both sides agree that immigrants who are ultimately denied asylum often defy deportation orders and stay in the United States illegally. Previous administrations did not make it a priority to find and deport them and instead focused on illegal immigrants who had committed serious crimes.