Three Republican U.S. senators have encouraged First Amendment challenges if the federal judiciary adopts a proposed rule that would require amicus filers to more broadly disclose financial ties to parties and non-parties.

The Supreme Court “has long protected those who associate for speech purposes from compelled disclosure of those associations, subjecting any such disclosures to ‘exacting scrutiny,’” Senate Minority Leader Mitch McConnell of Kentucky and Sens. John Thune of South Dakota and John Cornyn of Texas wrote in a letter Monday to the judiciary’s Committee on Rules of Practice and Procedure.