The Posse Comitatus Act limits the power of the federal government to authorize the use of military power during domestic conflicts. The Act was implemented post-Reconstruction in 1878 in order to prevent the involvement of the United States military during a law enforcement operation. The Act can be waived via an executive order. Some of the most notable waivers of the Posse Comitatus Act came by Bill Clinton in 1993 during the FBI standoff with Branch Davidians in Waco, Texas, and Ronald Reagan's order to round-up Cuban refugees in 1987.HowStuffWorks: The Posse Comitatus Act of 1878