A federal appeals court has found it was unconstitutional for Colorado to block an elector from voting for a candidate other than the winner of the state’s popular vote in 2016, which was Hillary Clinton, in a ruling that likely tees up more major court action about the Electoral College in advance of the 2020 presidential election.

“The text of the Constitution makes clear that states do not have the constitutional authority to interfere with presidential electors who exercise their constitutional right to vote for the President and Vice President candidates of their choice,” the federal appeals court in Colorado wrote in an opinion published Tuesday.

A state law in Colorado had forced its members of the presidential electoral college to vote in 2016 for the statewide winner, which was Democrat Hillary Clinton in 2016.