This is an FBI report on what to watch out for. Short blurb below.

They could be dismissed as a nuisance, a loose network of individuals living in the United States who call themselves “sovereign citizens” and believe that federal, state, and local governments operate illegally. Some of their actions, although quirky, are not crimes. The offenses they do commit seem minor: They do not pay their taxes and regularly create false license plates, driver’s licenses, and even currency.