The Trump administration is giving Immigration and Customs Enforcement officials the power to quickly deport migrants who were allowed into the country temporarily under Biden-era programs, according to an internal government memo obtained by The New York Times.

The memo, signed Thursday night by the acting head of the Homeland Security Department, offers ICE officials a road map on how to use expansive powers that were long reserved only for encounters at the southern border to quickly remove migrants. It also appears to give the officials the ability to expel migrants in two major Biden-era programs that have allowed more than a million people to enter the country temporarily.

Those programs — an app called CBP One that migrants could use to try to schedule appointments to enter the United States, and an initiative that let in certain migrants fleeing Cuba, Nicaragua, Venezuela and Haiti — were key pillars of the Biden administration’s efforts to discourage illegal entries by allowing certain legal pathways. Immigrant advocates also worried that the memo could apply to Afghan and Ukrainian immigrants brought to the United States under separate programs.

The decision indicates that President Trump will try to use every facet of the immigration enforcement apparatus to crack down on a system he has long said has been abused, and that he intends to target not just those who sneaked across the border but even those who followed previously authorized pathways to enter.

It is also sure to raise fears among a large class of immigrants, many of whom had fled desperate conditions, believed that they were in the country legally and might be afraid to return to their often-dangerous home countries.

Both of former President Joseph R. Biden Jr.’s signature programs had faced heavy criticism from Republicans, including Trump administration officials, as a way to facilitate illegal immigration through the guise of a government program. The migrants were given a grant to stay in the country for up to two years under a temporary legal status known as “parole.” The memo appears to allow for their deportation, regardless of whether they have reached the end of that legal status or still have time remaining.

In total, around 1.4 million migrants entered the country through the two programs since the beginning of 2023.

A senior Homeland Security official, speaking on the condition of anonymity, said the effort rested on Mr. Trump’s belief that Mr. Biden’s immigration programs were never lawful and that migrants in the country unlawfully should be removed quickly.

Stephen Miller, a White House deputy chief of staff and the architect of Mr. Trump’s hard-line immigration policies, has made clear that he opposed both programs.

“Here’s an idea: Don’t fly millions of illegals aliens from failed states thousands of miles away into small towns across the American Heartland,” Mr. Miller said on social media in September.

News of the memo was met with immediate criticism from immigrant advocates and former Biden officials.

“In addition to raising serious legal concerns, subjecting people who played by the rules to a summary deportation process is an outrageous and unprecedented betrayal,” said Tom Jawetz, a senior lawyer in the Homeland Security Department in the Biden administration.

Karen Tumlin, the director of the Justice Action Center, an immigrant advocacy group, said the decision was a mistake. She said she believed the memo could also allow ICE officials to try to deport migrants from Afghanistan and Ukraine.

“American communities have opened their hearts and homes for people from Cuba, Haiti, Nicaragua, Venezuela, Afghanistan and Ukraine,” she said. “Punishing people who did everything the government asked, and many of whom had U.S.-based sponsors, to this summary deportation procedure is appalling.”

Mr. Trump ordered the agency to shut down the Biden-era programs on Monday. That same day, Benjamine C. Huffman, the acting homeland security secretary, issued a separate memo ordering the phaseout of all such programs. On Tuesday, the administration widened the deportation powers.

On Thursday, Mr. Huffman provided additional guidance to the agency on the two key decisions and how they interact with each other.

In the memo, he directed ICE officials to analyze immigrants the agency is “aware of” who can be deported under the new fast deportations, which sidestep immigration courts, and consider whether they should be removed from the country. The memo suggests that officials prioritize immigrants who have been in the country longer than a year but who have not applied for asylum.

As part of that, the memo says that officials can, if necessary, decide to move to strip parole, a form of temporary legal status. Migrants brought under the two Biden-era programs — as well as other initiatives involving Afghans and Ukrainians — are in the country under that specific form of temporary status.

If migrants are already in the formal deportation process — which can take years — ICE officials can move to terminate their case and place them into the sped-up deportation program.

The memo also provides ICE officials the ability to target those who have been in the country under a temporary program but have remained more than two years for formal deportation proceedings.

The fast-track deportation powers have already been challenged in federal court in Washington by the American Civil Liberties Union. The lawsuit, filed Wednesday, argues that the decision violated federal law.

“The Trump administration wants to use this illegal policy to fuel its mass deportation agenda and rip communities apart,” Anand Balakrishnan, an A.C.L.U. lawyer, said in a statement. “Expanding expedited removal would give Trump a cheat code to circumvent due process and the Constitution, and we are again here to fight it.”