The federal government of the United States empowers a wide range of law enforcement agencies to maintain law and public order related to matters affecting the country as a whole.
Federal police possess enforcement authority as given to them under various parts of the United States Code (U.S.C.).
Federal law enforcement officers are authorized to enforce various laws generally only at the federal level. A few agencies have broad federal enforcement powers, but most enforce only narrow portions of federal law. In some cases, they may be empowered to enforce state and local law as well. These agencies have nationwide jurisdiction for enforcement of designated federal law. Federal agencies are limited by the U.S. Code to investigating matters that are explicitly within the power of the federal government. Some federal investigative powers have become broader in practice, since the passage of the USA PATRIOT Act in October 2001.
The Department of Justice was formerly the largest but remains the most prominent collection of law enforcement agencies, and handled most law enforcement duties at the federal level. It includes the United States Marshals Service(USMS), the Federal Bureau of Investigation(FBI), the Drug Enforcement Administration (DEA), and the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF), Federal Bureau of Prisons (BOP), and others.
In 2002, the Department of Homeland Security (DHS) was created by an act of Congress. DHS now includes the United States Secret Service (USSS), which protects the president and vice president of the United States, their families and other dignitaries as well as investigating counterfeiting crimes involving U.S. currency and monetary instruments; and U.S. Immigration and Customs Enforcement (ICE), which includes Enforcement Removal Operations (ERO) that handles interior immigration enforcement in the United States, and Homeland Security Investigations (HSI) which was created by the merger of the special agents of the former U.S. Immigration and Naturalization Service and the U.S. Customs Service.
There is also U.S. Customs and Border Protection (CBP) which includes United States Border Patrol (USBP), the CBP Office of Air and Marine (whose assets encompass the aviation and marine units of the old INS/Border Patrol and Customs Service), and which is the largest aviation/marine force in federal law enforcement; CBP officers are responsible for federal law enforcement at all U.S. Ports of Entry, including airports, sea ports, and the land border ports; USBP Agents are the primary enforcement unit along the U.S. international border between U.S. Ports of Entry; the Federal Protective Service (FPS) is responsible for federal law enforcement in federal buildings and properties.
Including elements of the U.S. Coast Guard and the U.S. Transportation Security Administration, DHS now has more sworn armed federal law enforcement agents and officers than any other department of the United States government.