The controversy over President Donald Trump’s appointment of Matthew Whitaker as acting U.S. attorney general moved to the U.S. Supreme Court on Friday, where advocates want the justices to resolve legal questions about the lawyer temporarily leading the U.S. Justice Department.

Veteran Supreme Court advocate Thomas Goldstein of Washington’s Goldstein & Russell filed a motion in a gun-related case asking the high court to substitute Deputy Attorney General Rod Rosenstein as acting attorney general and to decide the appointment question separate from the gun petition.