U.S. District Judge Naomi Reice Buchwald of the Southern District of New York has asked Justice Department attorneys to say how, exactly, President Donald Trump’s personal Twitter account differs from official accounts such as @POTUS and @WhiteHouse.

In a letter to the government’s attorneys Tuesday, Buchwald referred back to oral arguments held March 8 on summary judgment motions filed by both sides in Knight First Amendment Institute v. Trump. During the hearing, Buchwald’s questioning centered on Trump’s use of Twitter—which he famously has used in part to convey administration messages.