The sovereign citizen movement is a loose grouping of American, Canadian and Australian 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 government statutes or proceedings. They do not recognize United States currency, and maintain 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. The doctrines of the movement are similar to those of the freemen on the land movement more commonly found in Britain and Canada.
Many members of the sovereign citizen movement believe that the United States government is illegitimate. JJ MacNab, who writes for Forbes about anti-government extremism, has described the sovereign citizen movement as consisting of individuals who believe that the county sheriff is the most powerful law-enforcement officer in the country, with authority superior to that of any federal agent, elected official, or local law-enforcement official. This belief comes from the movement's origins in the white extremist group Posse Comitatus.
The Federal Bureau of Investigation (FBI) classifies some sovereign citizens ("sovereign citizen extremists") as domestic terrorists. In 2010, the Southern Poverty Law Center (SPLC) estimated that approximately 100,000 Americans were "hard-core sovereign believers", with another 200,000 "just starting out by testing sovereign techniques for resisting everything from speeding tickets to drug charges."
In surveys conducted in 2014 and 2015, representatives of US law-enforcement ranked the risk of terrorism from the sovereign citizen movement higher than the risk from Islamic extremism. Sovereign citizens have also been identified as a potential terrorist threat by the New South Wales Police Force in Australia.