The Supreme Court issued an unsigned order on Wednesday evening that effectively closes the United States’ southern border to nearly all Central American asylum seekers.

The decision stays a lower court decision blocking a Trump administration policy that seeks to halt nearly all asylum applications from these migrants and allow the US government to require them to seek asylum in countries they travel through. The government will now be allowed to enforce the policy while legal challenges move ahead.

The administration’s rule, issued on July 16, says that almost any foreign national who arrives at the southern border may not seek asylum if they crossed through another nation to get here. There are a few limits — a migrant can seek asylum in the United States if they complete a potentially onerous legal process in another country, for example, or if they were “severe” trafficking victims — but the practical effect of the rule is to ban most migrants from seeking asylum.