The US Supreme Court has ordered President Joe Biden to reinstate a policy of making asylum seekers stay in Mexico while claims are processed.
The policy was put in place by his predecessor, Donald Trump, as part of his measures to restrict the number of asylum seekers entering the US.
But Mr Biden suspended it on his first day of office.
Rights groups say the policy subjects migrants to dangerous conditions in Mexico’s border towns.
On Tuesday, the Supreme Court rejected a bid to block a Texas-based judge’s ruling requiring the government to revive the Migrant Protection Protocols (MPP) policy.
It said the Biden administration had “failed to show a likelihood of success” on the claim that rescinding the policy was not “arbitrary and capricious”.
The Biden administration can make another attempt to try and end the policy.
The American Civil Liberties Union has called on Mr Biden to try again and provide a “fuller explanation” for why the policy should be terminated.
Some 70,000 migrants were enrolled in the MPP policy. A month after Mr Biden’s inauguration, his administration began to gradually process these tens of thousands of people waiting in Mexico, allowing them into the US while their cases are heard.
It’s not yet clear how many people will be affected by the ruling.
The US Homeland Security department said it regretted the Supreme Court’s decision and would “continue to vigorously challenge it”.