Trump Starts Immigration Crackdown, Enlisting the Military and Testing the Law

President Trump’s flurry of executive actions on immigration in the hours after taking office was the leading edge of an effort to roll back four years of policies put in place by the Biden administration and reimpose an agenda that would fundamentally upend the United States’ global role as a sanctuary for refugees and immigrants.

In a series of orders he signed on Monday evening, Mr. Trump moved to seal the nation’s borders against migrants and systematically crack down on undocumented immigrants already in the United States, part of a policy barrage that included a national emergency declaration to deploy the military to the border and a bid to cut off birthright citizenship for the children of noncitizens.

While some of the orders were likely to face steep legal challenges and might be difficult or impossible to enforce, the directives sent an unmistakable message that Mr. Trump was serious about fulfilling his frequent campaign promises of clamping down on the border, and escalating an anti-immigration agenda that he has made the centerpiece of his political identity.

“With these actions we will begin the complete restoration of America and the revolution of common sense,” Mr. Trump said from the Capitol Rotunda after taking his oath of office. “All illegal entry will immediately be halted and we will begin the process of returning millions and millions of criminal aliens back to the places from which they came.”

Just minutes after Mr. Trump took the oath, his administration shut down a government program created by his predecessor that allowed migrants to secure appointments for admission into the United States through legal ports of entry through an app. Switching off the program, known as C.B.P. One, plunged about 30,000 migrants who had existing appointments to enter the United States into limbo, and indicated that it would now be far more difficult.

Hours later in the Oval Office, Mr. Trump moved to block asylum seekers and seal the border against those looking for protection in the United States. The Trump administration argued the illegal border crossings posed a national security and public health concern. Rather than citing a specific threat of disease, Mr. Trump simply said that migrants did not provide border authorities with “comprehensive health information,” posing a public health risk.

He declared a national emergency at the U.S.-Mexico border to allow him to circumvent Congress and unlock federal funding for border wall construction and other enforcement efforts. Mr. Trump appeared to go further than simply having the military support border authorities with construction. He also signed an order that gave the military an explicit role in immigration enforcement and directed the Defense Department to come up with a plan “to seal the borders and maintain the sovereignty, territorial integrity, and security of the United States by repelling forms of invasion.”

The directive would likely clash with an 1870s law called the Posse Comitatus Act, which generally limits the use of regular federal troops for domestic policing purposes.

“That is really dangerous and wrong-headed,” said Elizabeth Goitein, a senior director at the Brennan Center for Justice at New York University’s School of Law, who added that the order directed the military to treat the border not as a law enforcement matter but as a full-scale military campaign.

Mr. Trump took the steps even as the current state of the border is fairly calm, with crossings having fallen sharply after the Biden administration took major steps to limit migration.

Still, the executive actions, many of which Mr. Trump had previewed in recent years, are an attempt to make good on a promise to curtail immigration and enact mass deportations.

In another order issued on Monday, Mr. Trump declared that his government would no longer treat all U.S.-born children as citizens, signaling his intention to essentially ignore the constitutional guarantee of birthright citizenship. The order directed federal agencies, starting in 30 days, not to issue citizenship documents to U.S.-born children of an undocumented mother, or a mother on a temporary visa, if the father is not a U.S. citizen or permanent resident.

The move would amount to an extraordinary change of the 157-year-old 14th Amendment, and within hours it prompted a lawsuit from the American Civil Liberties Union.

Mr. Trump cannot abolish birthright citizenship on his own. Any change to the Constitution requires supermajority votes in Congress, and then ratification by three-quarters of the states. But denying certain immigrants’ children of citizenship documents would effectively mean that they could be barred from using public services, which could have the same effect as abolishing the right.

“What the Trump administration is readying goes well beyond immigration policy,” said Vanessa Cárdenas, executive director of America’s Voice, a pro-immigration think tank. “The push to gut 150 years of settled law and hard-won progress by attacking birthright citizenship, for example, seeks to reshape America’s future by moving this nation backwards.”

In front of thousands of supporters at Capital One Arena on Monday, Mr. Trump signed an order that rescinded an array of former President Joseph R. Biden Jr.’s immigration policies, including one that established a task force to reunite families separated by Mr. Trump’s zero-tolerance policy. Another restored Mr. Trump’s efforts to withhold federal funds from local agencies that refuse to cooperate with Immigrations and Customs Enforcement.

Mr. Trump is likely to issue more orders on immigration in the coming days, but there were already signs of substantial changes to the system in the immediate hours after his inauguration.

At the El Chaparral border crossing in Tijuana, Mexico, dozens of migrants stared at their phone screens trying to check whether their appointments were still valid and instead found a crushing message: “existing appointments have been canceled.”

“I am in shock,” said Maura Hernandez, who had arrived with her four small children and had an appointment scheduled for Tuesday.

“I don’t know what is going to happen to us,” she said, adding that they had fled their home amid rampant insecurity.

That was just one aspect of Mr. Trump’s Day 1 moves.

In one executive order, Mr. Trump also raised the prospect of imposing travel bans, similar to his first term. He directed his administration to take 60 days to identify countries where thoroughly vetting visitors and visa applicants is not feasible and poses a potential risk to national security. In those instances, the administration should consider whether there should be a full or partial ban on admitting people from those countries into the United States.

Mr. Trump also suspended refugee resettlement and enhanced the vetting of those seeking to come to the United States from overseas. He signed an executive order to end “catch and release,” which refers to the practice of releasing migrants into the United States to await a court appearance after they cross the border. The details of that order, like many of Mr. Trump’s actions, remain unclear.

Mr. Trump also designated drug cartels as terrorist organizations, enhancing his administration’s ability to target them.

The Biden administration had moved in June to bar asylum for migrants crossing into the country illegally. The order remained in place and border numbers dropped precipitously in recent months. Border agents used the order to quickly turn back migrants apprehended after crossing without authorization.

“All illegal aliens seeking entry into the United States should turn back now,” Stephen Miller, Mr. Trump’s deputy chief of staff and the architect of his anti-immigration agenda, wrote Monday on social media. “Anyone entering the United States without authorization faces prosecution and expulsion.”

Mr. Trump also said he would restore the so-called Remain in Mexico policy, which forced migrants to wait in the country until the date of their immigration case in court. The policy was a centerpiece of Mr. Trump’s first-term border crackdown. The Trump administration, however, will need the cooperation of Mexico to fully roll out the policy.

In a news conference Monday morning, Juan Ramón de la Fuente, Mexico’s foreign affairs minister, said that his country disagrees with the Remain in Mexico policy being reinstated, and that Mexico would have no obligation to process U.S. asylum requests if it were. Still, he said the country would find ways to operate “in the best way possible.”

Paulina Villegas contributed reporting from Tijuana, Mexico, Emiliano Rodríguez Mega from Mexico City and Eric Schmitt from Washington.