A more thorough explanation:

Emergency powers refer to the authority given to individuals in the executive branch to act outside of their usual authority in response to a danger that normal channels cannot address. The most important emergency powers are those given to the President through the National Emergencies Act. This act allows the President to declare a national emergency, which gives them a range of powers such as deploying troops or cutting off telecommunication in the country. There are over 120 statutory provisions that may be used by the President during a national emergency.

The Constitution does not expressly grant the President additional war powers or other powers in times of national emergency. However, many scholars think that the Framers implied these powers because the Executive Branch can act faster than the Legislative Branch. Nevertheless, the Judiciary cannot grant these powers to the Executive Branch when it tries to wield them because the Constitution remains silent on the issue. The courts will only recognize a right of the Executive Branch to use emergency powers if Congress has granted such powers to the President.

Presidents have claimed emergency powers at many pivotal points throughout United States history. For example, President Abraham Lincoln suspended habeas corpus without Congressional approval in 1861, claiming that the Confederate rebellion created an emergency that permitted him the extraordinary power of unilaterally suspending the writ. President Roosevelt invoked emergency powers when he issued Executive Order 9066 directing that all Japanese Americans residing on the West Coast be placed into internment camps during World War II. President Harry Truman declared the use of emergency powers in Executive Order 10340 when he seized private steel mills that failed to produce steel because of a labor strike in 1952.

The National Emergencies Act was enacted in 1976 in response to the continued existence of four declared national emergencies, the oldest of which had been in place for forty years. The Act enables the President to declare a national emergency and provides for a variety of termination methods, including the automatic termination of a national emergency upon its anniversary every year, if the President does not act to renew it.

Overall, emergency powers are a controversial topic because of the extent of the powers and the lack of express Constitutional grant. The extent of the Executive Branch's emergency powers has come under recent scrutiny.