What are Posse Comitatus and the Insurrection Act?

Posse Comitatus. Insurrection Act. Words that have been thrown around since President Trump threatened to unleash federal troops on cities seeing protests against police brutality and racism. Both have been the topics of online discussion.

So what are Posse Comitatus and the Insurrection Act?

Posse comitatus is Latin and means “the power or force of the county.” In its simplest form, the Posse Comitatus Act of 1878 states: “Whoever, except in cases and under circumstances expressly authorized by the Constitution or Act of Congress, willfully uses any part of the Army or the Air Force as a posse comitatus or otherwise to execute the laws shall be fined under this title or imprisoned not more than two years, or both.” The National Guard is exempt from this law because it is commanded by the state. However, the National Guard can be “federalized” if operating in federal capacity, in which case, it can violate Posse Comitatus.

It began as a sheriff’s ability to deputize any able-bodied man over the age of 15 for the purpose of enforcing the law. The Posse Comitatus Act was created after claims federal troops interfered with elections in Southern states during Reconstruction. So the Posse Comitatus Act limits the use of federal troops to be used for local law enforcement. Basically, federal troops can’t be used to execute the police’s duties. In theory.

There have been so many exceptions made to Posse Comitatus that the rule essentially has no teeth. The most powerful of those exemptions is the Insurrection Act.

The Insurrection Act allows the president to mobilize federal troops on American soil in four circumstances:
A state’s legislature or governor requests help because the state is experiencing an “insurrection … against its government” (10 U.S.C. § 251).

The president considers “unlawful” assemblies or rebellions to be interfering with the courts’ ability to enforce laws (10 U.S.C. § 252).

An “insurrection, domestic violence, unlawful combination, or conspiracy” prevents state or federal laws from being enforced in such a way that any class of people are denied their Constitutional rights and the state fails or refuses to protect those rights (10 U.S.C. § 253(1)).

Or, “any insurrection, domestic violence, unlawful combination, or conspiracy” that impedes the execution of laws or the course of justice (10 U.S.C. § 253(2)).

What happened in D.C. last week is almost certainly a violation of First Amendment rights. It is not, however, a violation of Posse Comitatus, as best we understand it. The D.C. National Guard are the only National Guard that answers directly to the federal government, but even so, it is largely exempt from Posse Comitatus. The unidentified officers believed to be from the Bureau of Prisons is the closest the Trump administration has come to crossing the line into violating Posse Comitatus. But as long as they don’t execute the duties of a police officer (like, say, making arrests), the rule is not violated. As one agent chillingly told a Politico reporter, “We can’t arrest you, but we can kill you.” And that, by the nature of our laws, is legal.