A federal appeals court ruled Tuesday that the Trump administration can make asylum seekers wait in Mexico for immigration court hearings while the policy is challenged in court, handing the president a major victory, even if it only proves temporary.

The 9th U.S. Circuit Court of Appeals — a frequent target of the president’s complaints — reversed a decision by a San Francisco judge that would have prevented asylum seekers from being returned to Mexico during the legal challenge.

The case must still be considered on its merits and could end up at the Supreme Court. But allowing the policy to remain in effect in the meantime lets the administration carry out an unprecedented change to U.S. asylum practices.

The administration has said it plans to rapidly expand the policy across the border, which would have far-reaching consequences for asylum seekers and Mexican border cities that host them while their cases wind through clogged U.S. immigration courts. Cases can take several years to decide.

The policy was challenged by 11 Central Americans and advocacy groups that argued it jeopardized asylum seekers by forcing them to stay in Mexico, where crime and drug violence are prevalent.

U.S. District Court Judge Richard Seeborg agreed April 8 and said the policy should be halted because it failed to evaluate the dangers migrants faced in Mexico.

The administration introduced its “Migrant Protection Protocols” policy on Jan. 29 in San Diego and later expanded it to Calexico, California, and El Paso, Texas. Under the policy, asylum seekers report to a border crossing in the morning. The U.S. government provides transportation to immigration court and returns them to the border after the hearing.