Here's a description from Wikipedia:
. . . [theh act] empowered the President to suspend the writ of habeas corpus to combat the Ku Klux Klan (KKK) and other white supremacy organizations during the Reconstruction Era. The act was passed by the 42nd United States Congress during the Reconstruction Era and signed into law by PresidentUlysses S. Grant on April 20, 1871. The act was the last of three Enforcement Acts passed by the United States Congress from 1870 to 1871 during the Reconstruction Era to combat attacks upon the suffrage rights of African Americans. The statute has been subject to only minor changes since then, but has been the subject of voluminous interpretation by courts.
The act marks a shift in the relationship between the national government and the states regarding law enforcement, so it adds to our understanding of the changing nature of federalism.
