The judges have long said they are deciding the fates of immigrants in a traffic-court setting. They wear robes, but do not have gavels. Instead, they pound date stamps on the pages of filings that come across their desks.

In April they were rattled when the Justice Department began requiring them to provide a detailed itinerary of upcoming foreign travel — car rental agencies, hotels and names of foreign nationals they were visiting — in order to maintain their security clearance. Although all executive branch employees with security clearences were required to submit the new information, the judges found it “invasive,” said Los Angeles Judge Ashley Tabaddor, speaking as the president of the union.

Other changes have been more substantive. In June, Attorney General Jeff Sessions issued a ruling making it more difficult for victims of domestic violence or gang violence to make asylum claims.

He also limited judges’ ability to put cases aside, for instance, while an immigrant sought legal status another way, such as by applying for a green card.

After a Philadelphia judge, Steven A. Morley, postponed a case because he thought the immigrant had not received proper notification, the Justice Department in July reassigned all of his 87 similar cases — saying it had reason to believe he had “committed potential violations” of law and policy. The union filed a grievance, arguing the government was trying to influence the outcome of the case.

Then, in August, Mr. Sessions declared that if judges saw it necessary to postpone a hearing — as they had in the past, for instance, to give a lawyer more time to prepare — they had to show “good cause.”

David Martin, a professor emeritus of law at the University of Virginia and a former lawyer for the Department of Homeland Security, said he understood the government’s perspective. He said immigration lawyers have used postponements to “string things out,” on the theory that the longer immigrants are in the country, the harder it is to deport them.