Questions about whether Native Americans born in the United States have birthright citizenship if they aren’t “subject to the jurisdiction” of the U.S. — such as if they live on sovereign tribal land — were raised in a U.S. Justice Department filing this week defending President Donald Trump’s executive order suspending such citizenship.

The president’s long-promised clampdown on immigration has begun, featuring actions like sending troops to the U.S.-Mexico border and ending birthright citizenship.