According to the USA Patriot Act, domestic terrorism are those which: "(A) involve acts dangerous to human life that are a violation of the criminal laws of the United States or of any State; (B) appear to be intended— (i) to intimidate or coerce a civilian population; (ii) to influence the policy of a government by intimidation or coercion; or (iii) to affect the conduct of a government by mass destruction, assassination, or kidnapping; and (C) occur primarily within the territorial jurisdiction of the United States.
Throughout history the KKK have commited crimes again the state and that would qualify them as a terrorist organization. By classfying them as a Terrorist organization the KKK will be force to disban and loss the protection of state police when conducting terrorist rallys