Federal law enforcement in the United States in the context of "Foreign Intelligence Surveillance Act"

The Federal Bureau of Investigation (FBI) is the primary federal law enforcement agency in the United States and also the American domestic intelligence and security service. An agency of the United States Department of Justice, the FBI is a member of the U.S. Intelligence Community and reports to both the attorney general and the director of national intelligence. A leading American counterterrorism, counterintelligence, and criminal investigative organization, the FBI has jurisdiction over violations of more than 200 categories of federal crimes. The FBI maintains a list of its top 10 most wanted fugitives.

Although many of the FBI's functions are unique, its activities in support of national security are comparable to those of the British MI5 and NCA and the Russian FSB. Unlike the Central Intelligence Agency (CIA), which has no law enforcement authority and is focused on intelligence collection abroad, the FBI is primarily a domestic agency, maintaining 56 field offices in major cities throughout the United States, and more than 400 resident agencies in smaller cities and areas across the nation. At an FBI field office, a senior-level FBI officer concurrently serves as the representative of the director of national intelligence.

The United States Immigration and Customs Enforcement (ICE; pronounced "ice") is a federal law enforcement agency under the supervision of the United States Department of Homeland Security. Its stated mission is to conduct criminal investigations, enforce immigration laws, preserve national security, and protect public safety. ICE was created as part of the Homeland Security Act of 2002 following the September 11 attacks. It absorbed the prior functions of the Immigration and Naturalization Service and the United States Customs Service.

ICE has been involved in multiple controversies throughout its existence, with significant increases in criticism during the first and especially the second administration of Donald Trump. Following the passage of the One Big Beautiful Bill Act in 2025 as part of Trump's hardline immigration policy, ICE became the largest and most well-funded federal law enforcement agency in U.S. history. Its aggressive and anonymized enforcement actions, controversial publicity campaigns, and militarization resulted in significant drops in public support and raised concerns over legality, lack of accountability, and civil rights violations. ICE agents are noted for wearing masks, civilian clothing, and using unmarked vehicles to protect their identity. The agency has been the subject of widespread protests particularly in 2018 and 2025, with some activists calling for its abolition. Since its expansion, the agency has been described by critics, as well as the American Civil Liberties Union, as a growing paramilitary force under Trump's personal control.

The United States Department of Justice (DOJ) is an executive department of the United States federal government that oversees the domestic enforcement of federal laws and the administration of justice. It is equivalent to the justice or interior ministries of other countries. The department is headed by the U.S. attorney general, who reports directly to the president of the United States and is a member of the president's Cabinet. Pam Bondi has served as U.S. attorney general since February 4, 2025.

The Justice Department contains most of the United States' federal law enforcement agencies, including the Federal Bureau of Investigation, the U.S. Marshals Service, the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Drug Enforcement Administration, and the Federal Bureau of Prisons. The department also has eight divisions of lawyers who represent the federal government in litigation: the Criminal, Civil, Antitrust, Tax, Civil Rights, Environment and Natural Resources, National Security, and Justice Management Divisions. The DOJ includes the U.S. Attorneys' offices for each of the 94 U.S. federal judicial districts.

The Federal Bureau of Investigation (FBI) is the domestic intelligence and security service of the United States and its principal federal law enforcement agency. An agency of the United States Department of Justice, the FBI is a member of the U.S. Intelligence Community and reports to both the attorney general and the director of national intelligence. A leading American counterterrorism, counterintelligence, and criminal investigative organization, the FBI has jurisdiction over violations of more than 200 categories of federal crimes. The FBI maintains a list of its top 10 most wanted fugitives.

Although many of the FBI's functions are unique, its activities in support of national security are comparable to those of the British MI5 and NCA and the Russian FSB. Unlike the Central Intelligence Agency (CIA), which has no law enforcement authority and is focused on intelligence collection abroad, the FBI is primarily a domestic agency, maintaining 56 field offices in major cities throughout the United States, and more than 400 resident agencies in smaller cities and areas across the nation. At an FBI field office, a senior-level FBI officer concurrently serves as the representative of the director of national intelligence.

United States Customs and Border Protection (CBP) is the largest federal law enforcement agency of the United States Department of Homeland Security. It is the country's primary border control organization, charged with regulating and facilitating international trade, collecting import duties, as well as enforcing U.S. regulations, including trade, customs, and immigration. CBP is one of the largest law enforcement agencies in the United States. It has a workforce of more than 45,600 federal agents and officers. It is headquartered in Washington, D.C.

The Transportation Security Administration (TSA) is an agency of the United States Department of Homeland Security (DHS) that has authority over the security of transportation systems within and connecting to the United States. It was created as a response to the September 11 attacks to improve airport security procedures and consolidate air travel security under a combined federal law enforcement and regulatory agency.

The TSA develops key policies to protect the U.S. transportation system, including highways, railroads, bus networks, mass transit systems, ports, pipelines, and intermodal freight facilities. It fulfills this mission in conjunction with other federal, state, local and foreign government partners. However, the TSA's primary mission is airport security and the prevention of aircraft hijacking. It is responsible for screening passengers and baggage at more than 450 U.S. airports, employing screening officers, explosives detection dog handlers, and bomb technicians in airports, and armed Federal Air Marshals and Federal Flight Deck Officers on aircraft.

In the United States, a special agent is an official title used to refer to certain investigators or detectives of federal, military, tribal, or state agencies who primarily serve in criminal investigatory positions. Additionally, some special agents operate in criminal intelligence, counterterrorism, or counterintelligence-based roles as well, with one or all of these roles occasionally taking precedence over criminal investigatory tasks.

Within the American federal law enforcement system, dozens of federal agencies employ federal law enforcement officers (LEOs), each with different criteria pertaining to the use of the titles special agent and agent. Most criminal investigators employed by the U.S. Department of Defense and its component departments typically utilize the title of "special agent."

The United States Secret Service (USSS or Secret Service) is a federal law enforcement agency under the Department of Homeland Security tasked with conducting criminal investigations and providing protection to American political leaders, their families, and visiting heads of state or government. The Secret Service was, until 2003, part of the Department of the Treasury, due to their initial mandate of combating counterfeiting of U.S. currency. The agency has protected U.S. presidents and presidential candidates since 1901.