In most cases, military forces are deployed to quiet the crowds, to secure government buildings and key or sensitive locations, and to maintain order.
Generally, military personnel replace civil authorities and perform some or all of their functions.
The constitution could be suspended, and in full-scale martial law, the highest ranking military General would take over, or be installed, as the military governor or as head of the government, thus removing all power from the executive, legislative, and judicial branches of the federal government.
The ability to suspend habeas corpus is often equated with martial law.
Article 1, Section 9 of the U.S. Constitution states, "The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it."
In United States law, martial law is limited by several court decisions that were handed down between the American Civil War and World War II.
In 1878, Congress passed the Posse Comitatus Act, which forbids military involvement in domestic law enforcement without congressional approval.
On October 1, 2002 United States Northern Command was established to provide command and control of Department of Defense homeland defense efforts and to coordinate defense support of civil authorities.
On June 15, 1995, Norman Olson, along with militia leaders from other states, testified before the United States Senate Subcommittee on Terrorism.
Olson's opening statement included the following:
"One other important point needs to be made. Since The Constitution is the limiting document upon the government, the government cannot become greater than the granting power. That is, the servant cannot become greater than its master. Therefore, should the chief executive or the other branch of government or all branches together act to suspend The Constitution under a rule of martial law, all power granted to government would be cancelled and differed back to the granting power. That is the people. And I'll conclude with this statement: Martial law shall NOT be possible in this country as long as the people recognize the bill of rights as inalienable."
Ex parte Milligan
On September 15, 1863, President Lincoln imposed Congressionally-authorized martial law.
The authorizing act allowed the President to suspend habeas corpus throughout the entire United States.
Lincoln imposed the suspension on "prisoners of war, spies, or aiders and abettors of the enemy," as well as on other classes of people, such as draft dodgers.
The President's proclamation was challenged in Ex parte Milligan, 71 US 2 [1866]).
The Supreme Court ruled that Lincoln's imposition of martial law (by way of suspension of habeas corpus) was unconstitutional.
The National Guard is an exception, since unless federalized, they are under the control of state governors.
This was changed briefly: Public Law 109-364, or the "John Warner Defense Authorization Act of 2007" (H.R.5122), was signed by President Bush on October 17, 2006, and allowed the President to declare a "public emergency" and station troops anywhere in America and take control of state-based National Guard units without the consent of the governor or local authorities.
Title V, Subtitle B, Part II, Section 525(a) of the JWDAA of 2007 reads "The [military] Secretary [of the Army, Navy or Air Force] concerned may order a member of a reserve component under the Secretary's jurisdiction to active duty.
The training or duty ordered to be performed...may include...support of operations or missions undertaken by the member's unit at the request of the President or Secretary of Defense."
The President signed the Defense Authorization Act of 2008 on January 13, 2008. However, Section 1068 in the enacted 2008 defense authorization bill (H.R. 4986: "National Defense Authorization Act for Fiscal Year 2008") repealed this section of PL 109-364.
New Orleans, Louisiana in the War of 1812 During the War of 1812, U.S. General Andrew Jackson imposed martial law in New Orleans, Louisiana after capturing the encampment of New Orleans from the British in the Battle of New Orleans.
The American Revolution as a result of the Boston Tea Party, King George III of Britain ordered martial law in Boston to keep riots and protest down.
The Territory of Hawaii
During World War II (1939 to 1945) what is now the State of Hawaii was held under martial law from December 7, 1941 to October 24, 1944.
Hurricane Katrina
Contrary to many media reports at the time, martial law was not declared in New Orleans in the aftermath of Hurricane Katrina, because no such term exists in Louisiana state law. However, a State of Emergency was declared, which does give unique powers to the state government similar to those of martial law. On the evening of August 31, 2005, New Orleans Mayor Ray Nagin nominally declared "martial law" and said that officers didn't have to observe civil rights and Miranda rights in stopping the looters. Federal troops were a common sight in New Orleans after Katrina. At one point, as many as 15,000 federal troops and National Guardsmen patrolled the city. Additionally it has been reported that armed contractors from Blackwater USA assisted in policing the city.
