In Shift, Biden Issues Order Allowing Temporary Border Closure to Migrants

President Biden issued an executive order on Tuesday that prevents migrants from seeking asylum at the U.S.-Mexico border when crossings surge, a dramatic election-year move to ease pressure on the immigration system and address a major concern among voters.

The order is the most restrictive border policy instituted by Mr. Biden, or any other modern Democrat, and echoes an effort in 2018 by President Donald J. Trump to cut off migration that was blocked in federal court.

The restrictions kick in once the seven-day average for illegal entries hits 2,500 per day. Daily totals already exceed that number, which means that Mr. Biden’s executive order could go into effect right away — allowing border officers to return migrants across the border into Mexico or to their home countries within hours or days.

Typically, migrants who cross illegally and claim asylum are released into the United States to wait for court appearances, where they can plead their cases. But a huge backlog means those cases can take years to come up.

The new system is designed to deter those illegal crossings.

The border would reopen to asylum seekers only when the number of crossings falls significantly. The figure would have to stay below a daily average of 1,500 for seven days in a row. The border would reopen to migrants two weeks after that.

The American Civil Liberties Union said it planned to challenge the executive action in court.

“The administration has left us little choice but to sue,” said Lee Gelernt, a lawyer at the A.C.L.U, which led the charge against the Trump administration’s attempt to block asylum in 2018 and resulted in the policy being stopped by federal courts. “It was unlawful under Trump and is no less illegal now.”