As of now, South Carolina legally
requires "subversives" to register with the government ($5 filing fee applicable), or face stiff fines and the possibility of prison time:
By "subversive organization," the law means "every corporation, society, association, camp, group, bund, political party, assembly, body or organization, composed of two or more persons, which directly or indirectly advocates, advises, teaches or practices the duty, necessity or propriety of controlling, conducting, seizing or overthrowing the government of the United States [or] of this State."
While the intention of the law is apparently aimed at Islamic terrorists, it's unclear in the law's wording whether it can be applied to right-wing militias, some of whom have reputedly called for the overthrow of the US government. The law states that "fraternal" and "patriotic" groups are exempt from the law, but only if they don't "contemplate the overthrow of the government."
Okay I'll say it: this reminded me the (Qld) Bjelke-Petersen Govt law, passed ('86?) a few years before their downfall (post-Corruption Enquiry), that made it illegal for "deviants" to be served in bars. The wording was somewhat nonspecific as to what exactly a deviant is/was, and I have no idea if it's ever been repealed.