The Michigan appeals court has blocked a 14-day extension to accept and count absentee ballots.
The court says any changes must rest with the Legislature, not the judiciary.
Michigan law says absentee ballots must be turned in by election night to be valid. But a Court of Claims judge had ordered that any ballots postmarked by Nov. 2 could be counted if they arrived within two weeks after the Nov. 3 election.
Attorney General Dana Nessel and Secretary of State Jocelyn Benson, both Democrats, had declined to appeal, leaving it to the Republican-controlled Legislature to intervene.