A federal judge on Monday rejected an attempt by lawyers for the far-right Oathkeepers group to toss out the heart of the federal government’s case against them: That they conspired to obstruct Congress’ formal certification of the election when they allegedly stormed the Capitol on Jan. 6.

U.S. District Judge Amit Mehta of the District of Columbia ruled that 17 Oathkeepers defendants must face charges of obstruction of an official proceeding and conspiracy to obstruct that proceeding. Mehta rejected arguments that the certification of the electoral college vote didn’t qualify as an “official proceeding” and that prosecutors’ description of their conduct didn’t violate that statute.