In the 1950's the heirarchy of the communist party in the US was convicted of planning the violent overthrow of the government. The case went to the US Supreme Court and their convictions were unheld even tho they were only issuing pamphlets on how to organize groups to plan the overthrow.
They were fined, jailed, and at last one was deported.
What happened between then and the 70s when these people plotting assassinations were allowed to go free.