The 1807 Act has been modified twice. In 1861, a new section was added allowing the federal government to use the National Guard and armed forces against the will of the state government in the case of "rebellion against the authority of the government of the United States," in anticipation of continued unrest after the Civil War. In 1871, the Third Enforcement Act revised this section () to protect Black Americans from attacks by the Ku Klux Klan. The language added at that time allows the federal government to use the act to enforce the Equal Protection Clause of the Fourteenth Amendment to the United States Constitution. This section of the act was invoked during the Reconstruction era, and again during desegregation fights during the Civil Rights Era.