Technically, according to the U.S. Constitution, America is forbidden from having a federal police force as the founding fathers wanted to keep policing to the state-level. However, due to the need to enforce laws and protect citizens, the federal government has woven together a group of specialized law enforcement agencies that act as federal police.
There are eight primary branches of federal police, each designated to rule over a specific area of crime or safety. They are, the Federal Bureau of Investigation (FBI); Central Intelligence Agency (CIA); Immigrations and Customs Enforcement (ICE); Bureau of Alcohol, Tobacco Firearms and Explosives (ATF); Department of Homeland Security; U.S. Drug Enforcement Administration (DEA); U.S. Secret Service (USSS); and the U.S. Marshall Service (USMS).
United States law governs what each entity can do and their jurisdictional guidelines. Some branches also govern tribal and state codes as well. The Patriot Act of 2001 has drastically changed some of the duties and functions of these federal police agencies.
Some additional agencies that took on even more responsibility for homeland security after 9/11 are the Immigration and Customs Enforcement - Homeland Security Investigations (HSI), the U.S. Coast Guard (USCG), the U.S. Transportation Security Administration (TSA), and the U.S. Customs and Border Protection (CBP).
The first form of federal police was the Postal Inspection Service which began in 1772. Then in 1789, the U.S. Marshals were formed through the Judiciary Act of Sept. 24, 1789. These first federal police agents were given the power to execute federal judicial writs and process. They also routinely brought outlaws in to be court marshaled or executed.
The FBI is the second oldest form of federal police in the nation. The FBI was assembled on July 26, 1908, by Charles Bonaparte, the second Attorney General under Roosevelt and upon formation it included just 34 agents.
The duties of federal police, regardless of the division and agency are extraordinarily specialized and tightly focused on one area of law enforcement.
Local and state police maintain the peace, protect the safety and security of citizens and respond to crime on a much smaller scale in their municipalities. They also have the power to arrest someone, perform searches and seize property, investigate crimes and respond in emergency situations. Sometimes they also interrogate suspects and provide testimony at trials.
The jobs of local police versus federal are very different. For example, the FBI and CIA may work on long-term investigations for many years gathering evidence to bring a criminal to justice. Local police may stop someone for drunk driving and hand out some other minor citations. Many federal police cannot arrest someone. Some simply gather facts, use high-tech equipment to monitor and enforce laws, but they do not operate as local police do. Local police work together with federal police in many instances. Generally, federal police have jurisdiction over local officers in high-risk cases like a hostage or terrorist situation.
Separated into dozens of specialized branches, federal police types vary and their jurisdictions and duties accordingly. The main eight branches are: