What is Martial Law and How Does it Work?
This pages is part of our larger Guide to What the Government Can and Can’t Do.
Martial law occurs when the military carries out civil government functions instead of the normal civilian elected government. It usually involves suspending civil laws and the civil court system, replaced by laws and rules dictated by the military.
In particular, civil rights and civil liberties may be suspended, such as the right to due process, including the procedures for properly convicting someone of a crime. The military may arrest and indefinitely detain individuals who are suspected of causing or contributing to disorder or other severe problem.
The purpose of martial law is that there is an extreme emergency in which there is not enough time or there is a breakdown in order such that it is not possible or practical to provide a proper trial or other rights to those accused of crimes.
The U.S. President and Congress have the power to impose martial law. However this power is limited by certain court cases, including Ex Parte Milligan and Duncan v. Kahanamoku. In Ex Parte Milligan, the Supreme Court ruled that President Lincoln’s imposition of martial law (by suspending the right of habeas corpus) was unconstitutional in areas where the local courts were still in session.
Governors also have the power to declare martial law within their states. A state of martial law is supposed to be temporary until the emergency is over.
In general, the U.S. military is not allowed to be involved with domestic law enforcement without the authorization of Congress. This is due to the Posse Comitatus Act of 1878.