Whether this is just stupid or a convenience arranged for law enforcement (see comment below about bigger punishment), my guess is that the definition of 'subversive activity' in the legislation is impractically broad. The SC legislature doesn't have the mandate to convict people of crimes (excepting impeachment of elected officials). Its members are not judges.

Besides treason, which by necessity has a very low rate of conviction (the last being CIA mole Robert Hanssen last decade), I don't see how wording like "overthrowing the government of the United State" could be upheld when there is no parallel in whatever offense one was actually convicted for.

Otherwise, levying fines like this is pretty blatant extrajudicial punishment.