(CNN) - 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.
One elector had cast his vote for then Ohio Republican Gov. John Kasich, causing the state to throw out his electoral vote. Two other Colorado electors who wanted to vote for Kasich then voted for Clinton.
The Kasich supporters sued Colorado in December 2016 for violating the US Constitution, according to the case file. A state court found the removal of the voter was proper just before their votes were cast officially that mid-December.
The faithless elector, Michael Baca, crossed out Clinton's name on his ballot to write in Kasich. So an elector who would vote for Clinton took his place. The Kasich supporters then went to federal court and lost at the trial level.
The US Court of Appeals for the 10th Circuit made the ruling in favor of Baca on Tuesday. The court also decided that Baca had the ability to bring his case and that it wasn't moot.
Colorado's then-Secretary of State Wayne Williams "impermissibly interfered with Mr. Baca's exercise of his right to vote as a presidential elector," the appeals court wrote. "Specifically, Secretary Williams acted unconstitutionally by removing Mr. Baca and nullifying his vote."
Colorado currently has nine electoral votes in presidential races and is often considered a battleground state, though it has trended Democratic in recent cycles. Clinton had won the state's popular vote in the general election, with 48.2% of the vote compared to Donald Trump's 43.3%. Kasich had challenged Trump unsuccessfully in the Republican presidential primaries.
Earlier this year, Colorado Gov. Jared Polis signed a law that would allot the state's electoral college votes to whichever candidate won the national popular vote.
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