WASHINGTON — Justice Department lawyers told the Supreme Court on Monday that President Trump acted lawfully in September 2017 when he decided to end an Obama-era program that protects young undocumented immigrants from deportation.
In a legal brief submitted to the court, the lawyers asserted that the president was fully within his rights to eliminate the program, known as Deferred Action for Childhood Arrivals, or DACA, and said the lower courts were mistaken when they said Mr. Trump’s action almost two years ago was arbitrary.
The Department of Homeland Security “correctly, and at a minimum reasonably, concluded that DACA is unlawful,” the lawyers argued, disputing the conclusions by the lower court judges about the three reasons the administration gave for ending the program. “None of those three grounds is remotely arbitrary or capricious, let alone all three.”
The Supreme Court is scheduled to hear arguments about the fate of the program in November. The justices could decide the case next spring or summer, just as the presidential election campaign is in full swing.
The government’s brief, filed late Monday, is the first salvo in what could be one of the biggest legal tests of the president’s immigration agenda. The outcome of the case will probably determine whether Mr. Trump can make good on a central campaign promise.
The court’s ruling, when it comes, could also energize partisans on both sides of the fierce debate over immigration. A decision to allow Mr. Trump to deport more than one million young people could galvanize immigrants to work against the president’s re-election.
But immigration is a central issue for Mr. Trump’s supporters, as well. A decision against the president could become a rallying cry on the right to argue that the Trump administration needs another four years to carry out its policies.
The future of DACA has been fiercely debated in Washington for years.
Under the program, undocumented immigrants who were brought to the United States as young children, often referred to as Dreamers, are temporarily shielded from deportation and allowed to live and work legally in the country. President Barack Obama created DACA in 2012 through executive action after Congress refused to pass legislation to grant the young immigrants permanent legal status.
As a presidential candidate, Mr. Trump argued that Mr. Obama’s actions were an abuse of power and repeatedly called for the program to end. In September 2017, Attorney General Jeff Sessions announced that Mr. Trump was terminating the program because the Supreme Court had found a related program for the parents of Dreamers to be unconstitutional.
“Simply put, if we are to further our goal of strengthening the constitutional order and the rule of law in America, the Department of Justice cannot defend this type of overreach,” Mr. Sessions said in a speech that month.
A federal judge blocked the administration from ending the DACA program and an appeals court upheld that action, ruling that the rationale officially given by the Department of Homeland Security for abandoning the program did not withstand scrutiny.
In the legal brief filed by the government on Monday, the Trump administration took issue with that assessment.
They noted that Kirstjen Nielsen, who was secretary of homeland security until April, provided the courts three separate reasons for why the department was no longer going to provide protection to the Dreamers.
The lawyers argued that the department properly was concerned that the program, which was similar to the one for the parents, would be found unconstitutional.
They also noted that “as a matter of policy, D.H.S. wanted to terminate a legally questionable nonenforcement policy and leave the creation of policies as significant as DACA to Congress.” That, they said in the brief, should be reason enough for the termination of the program to stand.
The government’s lawyers also rejected an argument made by the other side that Ms. Nielsen and Elaine Duke, the acting homeland security secretary who preceded Ms. Nielsen and officially terminated the program, were motivated by prejudice.
They said the “allegations are wholly insufficient to show that Secretaries Duke and Nielsen were motivated by racial animus in deciding to rescind a policy sanctioning the ongoing violation of federal immigration law by 700,000 aliens, especially given the serious questions about its legality.”
Lawyers for the groups seeking to keep DACA alive will file their briefs in the coming weeks.