That phrasing refers to a very broad set of movements and individuals. The usual core beliefs are:
Legislation in their jurisdiction and the government's authority to enforce it is in some way defective.
People in their jurisdiction can opt out of laws and government, and live only under "natural law".
People have to perform a set of legal procedures (spells, effectively) in order to achieve that.
Exactly why and how law/government authority is defective, how they understand natural law, what the spells are that they have to cast - all of these are extremely variable both between jurisdictions and between individuals.
Primarily it's a set of grifters charging money for courses and materials to learn about these beliefs from whoever they can convince. Sometimes, as in Germany, it's a group of neo-Nazis plotting to reinstate the Kaiser.