In Ex Parte Yarbrough, also known as the Ku Klux Klan cases, the U.S. Supreme Court upholds the convictions of Ku Klux Klan members who were tried under federal civil rights statutes for the beating and intimidation of people seeking to vote in a congressional election. The Court finds that the power to protect voters comes from the authority assigned to Congress in the Constitution.
Even though the states primarily had protected the right to vote in federal elections before the federal law, the Court says the federal government has the authority to protect voting in federal elections when necessary.