It has power to suspend laws, more entire populations, arrest and detain citizens without a warrant and hold them without trial. It can seize the property, food supplies, transportation systems, and can suspend the Constitution of the US.
Not only it is the most powerful entity in the United States, but it has not even created under Constitutional law by the Congress. It was a product of a Presidential Executive Order.
No, it is not the US Military nor the Central Intelligence Agency, they are subject to Congress.
FEMA had the original concept when it was created, to assure the survivability of the United States government in the event of a nuclear attack on this nation.
FEMA then would have the right to order the detention of anyone whom there is reasonable ground to believe will engage in, or probably conspire with others to engage in acts of espionage or sabotage.
The plan also authorized the establishment of concentration camps for detaining the accused, but no trial. An Executive Order signed by then President Bush in 1989 authorized the Federal Emergency Management Agency to build 43 primary camps (having a capacity of 35.000 to 40.000 prisoners each) and also authorized hundreds of secondary facilities.
It is interesting to note that several of these facilities can accommodate up to 100.000 prisoners. These facilities have been completed and are already manned but, as yet, contain no prisoners.
There over 600 prison camps in the US, all fully operational and ready to receive prisoners. They are all stuffed and even surrounded by full-time guards, but they are empty.
These camps are to be operated by FEMA should Marital law need to be implemented in the United States."
Source: Electronic Media Monitoring 2002.
See also FEMA - The Secret Government, by Harry V. Martin & David Caul