Militias in America date back to colonial times, when citizens agreed to provide their services and firearms for mutual defense. Today, militias consist of two types: government-sanctioned state militias and private citizen militias that are unaffiliated with government.

The citizen militia movement has grown rapidly during the 1990s, particularly in western states. Citizen militias in 1996 totaled 441 groups in fifty states, according to the Southern Poverty Law Center, a civil rights organization based in Montgomery, Alabama. These groups adhere to a variety of beliefs, from what many observers have called a paranoid distrust of government to endorsement of white supremacy to espousal of the right to own firearms. Law enforcement and other experts assert that, although widespread, militia members are well connected through computer networks, public forums, radio broadcasts, videos, and numerous publications.

Media and public attention toward citizen militias increased following several high-profile incidents. Militia members and other...