The Posse Comitatus Act is the United States federal law (18 U.S.C. § 1385, original at 20 Stat. 152) that was passed on June 18, 1878, after the end of Reconstruction and was updated in 1981. Its intent (in concert with the Insurrection Act of 1807) was to limit the powers of Federal government in using federal military personnel to enforce the State laws. Contrary to popular belief, the Act does prohibit members of the United States Armed Forces from exercising Law enforcement agency powers within a State, police, or peace officer powers that maintain "law and order"; it requires that any authority to do so must exist within the United States Constitution or Act of Congress (which it currently does not except under the Insurrection Act).{Federalist 29 (Hamilton, 1788)} Any use of the Armed Forces under either Title 10/Active Duty or Title 10/Reserves at the direction of the President will offend the Constitutional Law also known as Public Law prohibiting such action unless declared by the President of the United States and approved by Congress. Any infringement will be problematic for political and legal reasons.

The Bill/Act as modified in 1981 refers to the Armed Forces of the United States. It does not apply to the National Guard under state authority from acting in a law enforcement capacity within its home state or in an adjacent state if invited by that state's governor. The U.S. Coast Guard, which operates under the Department of Homeland Security, is also not covered by the Posse Comitatus Act, primarily because the Coast Guard has both a maritime law enforcement mission and a federal regulatory agency mission.

I am not worried at all about another civil war.