A federal judge said on Wednesday that the deportation of immigrants by the Trump administration to Libya would be in violation of a court order he issued in March, creating a legal impediment to what would be a sharp escalation of President Trump’s immigration crackdown.

The written order, by Judge Brian E. Murphy of Massachusetts, was in response to a request from immigration lawyers to block what they said was a planned U.S. military flight to transport a group of Laotian, Vietnamese and Filipino migrants to North Africa.

The lawyers, citing accounts from their migrant clients, who had been told they would be deported to Libya this week, argued that the removals would “blatantly” defy a previous order by Judge Murphy requiring migrants be provided at least 15 days to contest deportations to places other than their countries of origin if they had reason to fear being sent there.

The judge agreed.

“If there is any doubt — the Court sees none — the allegedly imminent removals, as reported by news agencies and as Plaintiffs seek to corroborate with class-member accounts and public information, would clearly violate this Court’s Order,” wrote Judge Murphy, a Biden appointee.

The filing came after U.S. officials said on Tuesday that the Trump administration was planning to transfer migrants to Libya on a U.S. military plane. They said the flight could have left as soon as Wednesday, depositing the migrants in a country that has been racked with conflict and divided for years between two hostile administrations.

But after the plans were made public in news reports on Tuesday evening, the administration faced pushback. Libya’s rival governments both denied on Wednesday that they had agreed to receive deported immigrants from the United States, saying this would violate the North African nation’s sovereignty.

It was unclear on Wednesday afternoon whether the Trump administration would move ahead with the flight to Libya. Mr. Trump did not directly answer a question about deportations to the nation on Wednesday. White House officials declined to comment on Judge Murphy’s order or deportation flights to Libya.

The decision to move ahead with the deportations to Libya would be striking, even for an administration that has already sent hundreds of migrants to a terrorism prison in El Salvador.

Libya operates numerous detention facilities for migrants that Amnesty International branded a “hellscape” in a 2021 report, saying it had found evidence of sexual violence against both adult and child prisoners.

But Mr. Trump’s aides hope such deportations will spread fear among undocumented immigrants still in the United States and encourage them to leave voluntarily.

The number of detainees and nationalities of those at risk of being sent to Libya remained unclear. But in recent days, the Trump administration had pushed Libya to accept migrants from various nations, according to an administration official familiar with the matter.

The push by the United States included a proposal for Libya to accept more than two dozen detainees from other nations, the official said. The agreement has not been finalized.

In court filings on Wednesday, immigration lawyers said they had heard from migrants detained in South Texas who were told by immigration officials that they needed to sign a document agreeing to be deported to Libya.

“When they all refused, they were each put in a separate room and cuffed in (basically, solitary) in order to get them to sign it,” wrote Trina Realmuto, a lawyer with the National Immigration Litigation Alliance.

Another lawyer heard from a Laotian man who learned he might be deported to Saudi Arabia or Libya and was then moved out of the detention center in Pearsall, Texas.

Ms. Realmuto and other lawyers argued the deportations would violate a temporary order issued by Judge Murphy in March requiring the government to give migrants who have a “final order of removal” at least 15 days to contest deportation to so-called third-party nations.

“Any Class Member who is removed to Libya faces a strong likelihood of imprisonment followed by torture and even disappearance or death,” Ms. Realmuto said. “Indeed, given Libya’s human rights record, it is inconceivable that Class Members from other countries would ever agree to removal to Libya, but instead would uniformly seek protection from being removed to Libya.”

The Trump administration has continued to deport people to so-called third-party countries, despite Judge Murphy’s previous order. The administration for example has continued to send Venezuelans to a terrorism prison in El Salvador — although those cases have been challenged on another legal basis: because the Venezuelans were expelled from the United States under an 18th-century wartime law known as the Alien Enemies Act.

The administration has defended the removals, saying they do not violate the court order because Judge Murphy’s ruling applies only to officials in the Department of Homeland Security and those Venezuelan detainees were sent by officials in the Defense Department.

The administration appeared to be using the same playbook as they planned to send migrants to Libya on a military plane. But Judge Murphy also warned last month that his order applied to every federal agency. Each one, he said, including the Pentagon, needed to provide sufficient notice to migrants before removing them to a third nation.

Erika Solomon, Islam Al-Atrash, Hamed Aleaziz and Alan Feuer contributed reporting.