A federal judge heard oral arguments Monday over the legality of the Trump administration’s latest travel restrictions, pushing the parties for some sort of standard to evaluate the limits of presidential authority.

In a hearing before the U.S. District Court for the District of Maryland, Judge Theodore Chuang pressed government lawyer Hashim Mooppan and the opposing lawyers, Omar Jadwat of the American Civil Liberties Union, Justin Cox of the National Immigration Law Center, Gadeir Abbas of the Council on American-Islamic Relations and Mark Mosier of Covington & Burling, on when and how the president exceeds his authority under immigration law.