Posse Comitatus

The term posse comitatus describes a group of able-bodied people formed – usually by a sheriff – for the purpose of defending the country, or to prevent others from breaking the law. Authorities no longer rely on posse comitatus, though the concept still exists as part of the American legal system. For example, a posse comitatus formed up in 2018, and headed to the Mexican border to enforce immigration law. To explore this concept, consider the following posse comitatus definition.

Definition of Posse Comitatus


  1. A group of people formed by a sheriff to defend the country and prevent people from breaking the law.


Mid-17th century          Medieval Latin (translates to “power” or “force of the county”)

History of Posse Comitatus

The Army is responsible for the creation of the Posse Comitatus Act. Congress created this legislation in response to the military’s occupation of the former Confederate States during Reconstruction (1865-1877). During the Compromise of 1877, Republicans agreed to withdraw federal troops from Florida, Louisiana, and South Carolina in exchange for the states certifying Rutherford B. Hayes as the next President of the United States. This came after Samuel J. Tilden, a Democrat from New York, had beaten Hayes fair and square in the election.

The Constitution awards the states, not the federal government, the power to decide an election. Therefore, following this incident, the U.S. representatives from the former Confederate States immediately agreed to prioritize legislation preventing similar incidents in the future. Specifically, they agreed to draft a law that would prevent U.S. Presidents and Congress from imposing federal troops upon any U.S. state. In 1878, the Democratic Congress passed this law, which became the Posse Comitatus Act.

Posse Comitatus Act

The Posse Comitatus Act is a law that President Rutherford B. Hayes signed in June of 1878. The purpose of the Posse Comitatus Act is to limit the federal government’s authority to intervene in domestic policies within the U.S. The Act initially only applied to the U.S. Army. However, officials amended it in 1956 to include the U.S. Air Force. The Act does not specifically mention the U.S. Navy; however, the Navy has arranged for regulations to cover their policies as well.

The Lattimer Massacre

Before slavery became a hotly contested issue, the government only rarely relied on posse comitatus to enforce order. However, posse comitatus soon became responsible for violent and illegal actions, including lynchings. One of the earliest examples of posse comitatus in history occurred in September of 1897 in an event known as the Lattimer massacre. In fact, the Lattimer massacre is the reason why law enforcement no longer relies on a posse comitatus to quiet the people during moments of civil unrest, like during peaceful strikes.

During the Lattimer massacre, a Luzerne County posse comitatus, organized by the sheriff, shot and killed at least 19 unarmed striking coal miners. They also wounded numerous others. Since then, America has relied on posse comitatus only as a method of local self-governance. The posse comitatus now functions by the will of the people, not in response to them. Today, some states have repealed posse comitatus by statute, however it is still alive in well in states like Georgia.

Exceptions to the Posse Comitatus Act

There are several exceptions to the Posse Comitatus Act. Generally, exceptions to the Posse Comitatus Act require federal and domestic forces to come together for the benefit of the greater good. For example, under U.S. Code 18 U.S.C. § 831, the Attorney General can request help from the Secretary of Defense in domestic law enforcement situations.

For instance, situations involving threats like nuclear weapons may require “back-up” from federal forces. In a situation like this, the Department of Defense has the power to provide authorization to whomever it deems fit, provided that the person does not interfere with U.S. military preparations.

Another exception to the Posse Comitatus Act occurs when federal and domestic law enforcement work together during operations involving drugs or counter-terrorism. In these cases, the two forces can exchange such services as surveillance and intelligence gathering, as well as equipment.

Posse Comitatus Example Involving the Baltimore Riots

An example of posse comitatus appears in the case of Mayor and City Council of Baltimore, et al. v. Silver, et ux. (1971). This case relates to the riots that broke out in the city of Baltimore in April of 1968 in reaction to the assassination of civil rights leader Martin Luther King, Jr. As a result of the damages that the rioters caused, citizens and corporations filed around 400 lawsuits against the Mayor and the City Council of Baltimore.

Decision of the Lower Court and Appeal

The City filed a motion for summary judgment, which the court subsequently denied. The City then filed an appeal with the Court of Appeals of Maryland. While the citizens argued that perhaps a posse comitatus might have been able to control the rioters and prevent or at least limit the damage they caused, the City disagreed.

In its appeal, the City argued that, not only would a posse comitatus be out of place in this modern age, but it would have done little to calm or quiet the situation. Further, the City raised the point that such a group would have actually gotten in the way of the police and impeded their ability to do their jobs. Ultimately, the Court of Appeals affirmed the lower court’s denial of the City’s motion for summary judgment and remanded the case back to the lower court. Specifically, the Court wrote:

“The City in its brief makes the request that should this Court affirm the lower court’s refusal to grant its motion for a summary judgment, that we not affirm the dismissal of its petition for declaratory judgment but remand the case for further proceedings within the framework of declaratory relief. We are not disposed to do this. We cannot conceive of further proceedings being pursued which would not result in an evidentiary hearing in which there would be facts in dispute. Such proceedings would, in our opinion, be an impermissible extension of the purposes of declaratory relief as contemplated under Code, Article 31A…Accordingly, while affirming the lower court’s denial of the City’s motion for summary judgment, we are remanding the case for the limited purpose of having the lower court restate its order including therein a declaration of the rights of the parties according to the views expressed in this opinion.”

Related Legal Terms and Issues

  • Congress – The legislative branch of the United States federal government, composed of the House of Representatives and the Senate.
  • Remand – To return a case to a lower court for reconsideration.
  • Strike – The refusal to work by a group of employees as a form of protest, typically as a way to gain something of value from their employer, such as a pay increase.
  • Summary Judgment – A final decision on the case, handed down by the judge on the basis of the statements and evidence presented, without a full trial.