At issue is the "Purcell principle," a 20-year-old rule warning federal courts against changing voting rules close to an election, reported CNN. Every time the court has invoked Purcell before, it's used the doctrine to stop federal courts from overriding state election rules — a protection rooted in federalism. Trump's executive order would scramble that logic by requiring the U.S. "This mail voting executive order sits on the wrong side of the line," said ACLU Voting Rights Project director Sophia Lin Lakin. "It's a federal actor imposing late-breaking changes on state election systems over the objections of the states that run them."