A Trump administration immigration policy that requires asylum seekers to wait in Mexico while their cases wind through U.S. courts was blocked and then reinstated by a court in the matter of hours, creating chaos at border crossings, courtrooms and legal offices.

A three-judge panel of the 9th U.S. Circuit Court of Appeals put the policy on hold midday Friday, delivering a setback to a policy that has become one of President Donald Trump’s signature efforts to restrict immigration.

But by the end of the day, the court allowed the program to go back into effect after the Justice Department argued that its suspension will prompt migrants to overrun the border and endanger national security. The White House argued that the suspension of the policy would overwhelm the nation’s immigration system, damage relations with the government of Mexico and increase the risk of outbreak from the new coronavirus.

Customs and Border Protection closed one border crossing leading into El Paso after the initial decision. Government attorneys said immigration lawyers had begun demanding that asylum seekers be allowed in the United States, with one insisting that 1,000 people be allowed to enter at one location.

The program was instituted last year and has sent about 60,000 asylum seekers back to Mexico. Immigration lawyers and advocates say the program is a humanitarian disaster, subjecting migrants to violence, kidnapping and extortion in dangerous Mexican border cities. Hundreds more have been living in squalid encampments just across the border.