Attorneys for former President Donald Trump moved a lawsuit seeking to bar him from running again for the White House from state to federal court in the first step of what promises to be a tangled legal battle that seems ultimately destined for the U.S. Supreme Court.

The liberal group Citizens for Responsibility and Ethics in Washington filed the initial lawsuit on Wednesday in Colorado state court, arguing a Civil War-era clause prohibiting higher office for those who once swore an oath to the Constitution and then engaged in 'insurrection' prevents Trump from running in 2024. Trump's attorneys on Thursday moved the case to federal court.