It can also be used as a rationale for suspending civil liberties.
Such declarations usually come during a time of natural disaster, during periods of civil disorder, or following a declaration of war.
A state governor or local mayor may declare a state of emergency within his or her jurisdiction. This is common at the state level in response to natural disasters.
The president of the United States, as head of the executive branch, has the authority to declare a federal state of emergency.
The only emergency provisions in the U.S. Constitution are: "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." and an exemption from the privilege of a grand jury hearing for cases arising in the military when in service in a time of "public danger".
Habeas corpus was suspended on April 27, 1861 during the American Civil War by Abraham Lincoln in parts of Maryland and some midwestern states, including southern Indiana.
He did so in response to demands by generals to set up military courts to rein in "copperheads", those in the Union who supported the Confederate cause.
Lambdin P. Milligan and four others were accused of planning to steal Union weapons and invade Union prisoner-of-war camps, and were sentenced to hang by a military court in 1864. However, their execution was not set until May 1865, so they were able to argue the case after the Civil War.
It was decided in the Supreme Court case Ex Parte Milligan 71 US 2 1866 that the suspension was unconstitutional because civilian courts were still operating, and the Constitution only provided for suspension of habeas corpus if these courts are actually forced closed.
On December 16, 1950, during the Korean War, President Truman issued Presidential Proclamation No. 2914, declaring a state of national emergency.
The Supreme Court ruling in Youngstown Sheet & Tube Co. v. Sawer established in1952 during this emergency that presidents may not act contrary to Acts of Congress during an emergency.
During the Watergate scandal which erupted in the 1970s after president Richard Nixon allowed illegal actions, Congress investigated the extent of the President's powers and belatedly realized that the U.S. had been in a continuous state of emergency since 1950.
As a result, in 1976 the National Emergencies Act set a limit of two years on emergency declarations unless the president explicitly extends them, and requiring the president to specify in advance which legal provisions will be invoked.
The Act terminated the emergency of 1950 on September 14, 1978; however, even in the 21st century, the federal courts have upheld harsh penalties (including deportation) for crimes that occurred during the state of national emergency from 1950 to 1978, where the penalties were escalated because of the existence of that emergency.
The 1977 International Emergency Economic Powers Act allows freezing of assets, limiting of trade, and confiscation of property during a declared emergency.
A federal emergency declaration allows the United States Federal Emergency Management Agency (FEMA) to exercise its power to deal with emergency situations; federal assistance also becomes available to areas that are declared to be in a state of emergency.
For FEMA, emergency declarations are different from the more common disaster declarations done for hurricanes and floods.
Typically, a state of emergency empowers the executive to name coordinating officials to deal with the emergency and to override normal administrative processes regarding the passage of administrative rules.
The United States is formally in an ongoing (and effectively permanent limited state of emergency declared by several Presidents for several reasons.
A state of emergency began on January 24, 1995 with the signing of Executive Order 12947 by President Bill Clinton.
In accordance with the National Emergencies Act, the executive order's actual effect was not a declaration of a general emergency, but a limited embargo on trade with "Terrorists Who Threaten To Disrupt the Middle East Peace Process".
This "national emergency" was expanded in 1998 to include additional targets such as Osama bin Laden, and has been continued to at least 2008 by order of President George W. Bush.
There are a number of other ongoing national emergencies of this type, referenced at and, regarding for instance diamond trade with Sierra Leone.
Especially noteworthy are the ongoing states of emergency declared on November 14, 1979 regarding the Iran Hostage Crisis., that declared on March 15, 1995 with respect to Iran, and that declared on September 14, 2001 through Bush's Proclamation 7463, regarding the terrorist attacks of September 11, 2001.
President Barack Obama declared on 24 Oct 2009 a National Emergency for Swine Flu, aiming to increase abilities for hospitals and medical centers to handle "swine flu" cases, responding to CDC reports stating that swine flu has become widespread in 46 of 50 U.S. states.
