Federal law enforcement grew piece by piece as Congress made new federal crimes, from the Marshals Service in 1789 to the FBI in 1908 and the Drug Enforcement Administration in 1973. Each agency has its own jurisdiction, though many overlap, and they work with state and local police through task forces and shared databases.
This guide explains the main agencies, what they do, how they are organized and overseen, and the debates about federal policing.
In 2025 and 2026 the administration reassigned agents from the FBI, DEA, ATF, and other agencies to immigration enforcement and proposed restructuring some agencies. Supporters said the shifts addressed urgent priorities and that agencies had grown inefficient, while critics said they diverted resources from violent crime, terrorism, and drug cases. Long-running debates include the independence of the FBI and prosecutors from political direction, the expansion of federal crimes, the use of task forces with local police, and civil liberties concerns about surveillance.
The Drug Enforcement Administration, created in 1973, enforces federal drug laws at home and abroad. The Bureau of Alcohol, Tobacco, Firearms and Explosives, moved from Treasury to Justice in 2003, regulates the firearms industry and investigates gun and arson crimes. The U.S. Marshals Service, the oldest federal law enforcement agency, protects federal courts, hunts fugitives, transports prisoners, and runs the witness protection program. The Bureau of Prisons holds about 155,000 people in federal custody.
The Constitution gives the federal government no general police power, so federal law enforcement rests on specific powers such as regulating interstate commerce, collecting taxes, and controlling borders. The Bureau of Justice Statistics counted roughly 137,000 full-time federal officers authorized to make arrests and carry firearms in 2020, spread across about 90 agencies. Most are in the Justice and Homeland Security departments, but agencies from the Postal Service to the Interior Department and many inspectors general have armed agents.
The Federal Bureau of Investigation, founded in 1908, is the principal investigative arm of the Justice Department and the lead domestic counterterrorism and counterintelligence agency. It has about 13,000 special agents and investigates crimes from public corruption and cyber attacks to violent crime and civil rights violations. Its director serves a single 10-year term, adopted in 1976 after J. Edgar Hoover's 48 years leading the bureau and its predecessor, to limit the director's power and political influence.
The 93 U.S. attorneys prosecute federal crimes in their districts under the direction of the Attorney General, and the Justice Department's criminal and national security divisions handle major cases. Agencies are overseen by inspectors general, congressional judiciary and homeland security committees, and the courts, which enforce constitutional limits on searches, interrogations, and prosecutions. The Posse Comitatus Act generally bars the military from domestic law enforcement.
Customs and Border Protection is the largest federal law enforcement agency, guarding ports of entry and the borders. Immigration and Customs Enforcement enforces immigration law in the interior and, through Homeland Security Investigations, investigates smuggling and trafficking. The Secret Service protects the President and other leaders and investigates financial crimes. The Coast Guard, Transportation Security Administration, and Federal Protective Service also have enforcement roles. A 2025 budget law provided large funding increases for immigration enforcement.
See the immigration side in who handles immigration, explore the agencies that protect the country in the homeland security agencies, or learn who watches the watchers in federal watchdogs.