International Emergency Economic Powers Act: Origins, Evolution, and Use [Updated July 14, 2020] [open pdf - 2MB]
From the Summary: "The International Emergency Economic Powers Act (IEEPA) provides the President broad authority to regulate a variety of economic transactions following a declaration of national emergency. IEEPA, like the Trading with the Enemy Act (TWEA) from which it branched, sits at the center of the modern U.S. sanctions regime. Changes in the use of IEEPA powers since the act's enactment in 1977 have caused some to question whether the statute's oversight provisions are robust enough given the sweeping economic powers it confers upon the President during a declared emergency."
CRS Report for Congress, R45618
Congressional Research Service: https://crsreports.congress.gov/