United States administrative law encompasses statutes, common law, and directives issued by the Office of Information and Regulatory Affairs in the Executive Office of the President, that together define the extent of powers and responsibilities held by administrative agencies of the United States Government (both executive branch agencies and independent agencies). The executive, legislative, and judicial branches of the U.S. federal government cannot always directly perform their constitutional responsibilities. Specialized powers are therefore delegated to an agency, board, or commission. These administrative governmental bodies oversee and monitor activities in complex areas, such as commercial aviation, medical device manufacturing, and securities markets.