What’s a sovereign citizen you ask? According to Infogalactic:
The sovereign citizen movement is a loose grouping of American and Canadian litigants, commentators, tax protesters and financial-scheme promoters. Self-described sovereign citizens take the position that they are answerable only to their particular interpretation of the common law and are not subject to any statutes or proceedings at the federal, state or municipal levels; that they do not recognize United States currency; and/or that they are “free of any legal constraints.” They especially reject most forms of taxation as illegitimate. Participants in the movement argue this concept in opposition to “federal citizens,” who, they say, have unknowingly forfeited their rights by accepting some aspect of federal law.
What’s that look like in practice? Mister Metokur has made a handy educational video (language warnings, etc. etc.).
(That cop that breaks the window with his bare hands? Badass.)