A federal judge in Pennsylvania ruled in favor of President Donald Trump‘s use of the Alien Enemies Act, marking the first time a judge has approved of the centuries-old law as a tool for expediting deportations of some illegal immigrants.

U.S. District Judge Stephanie L. Haines, who was nominated by President Donald Trump, is the first judge to back the Trump’s use of the 1798 Alien Enemies Act.

The ruling, applying only to detainees held in western Pennsylvania, is the first to uphold the president’s invocation of the wartime act. But it requires that detainees be given 21 days’ notice.