A federal judge in Massachusetts on Thursday blocked key portions of President Donald Trump’s executive order seeking to tighten rules governing mail-in voting, ruling the president lacked constitutional authority to impose the changes on states ahead of this year’s midterm elections.

U.S. District Judge Indira Talwani issued a preliminary injunction halting implementation of several provisions in Trump’s March executive order, which sought to create federal voter eligibility lists and restrict the delivery of mail ballots.