<P> Policing in the United States is conducted by "close to 18,000 federal, state, local and city departments". Every state has its own nomenclature for agencies, and their powers, responsibilities and funding vary from state to state . </P> <P> At the federal level, there exists both federal police, who possess full federal authority as given to them under United States Code (U.S.C.), and federal law enforcement agencies, who are authorized to enforce various laws at the federal level . Both police and law enforcement agencies operate at the highest level and are endowed with police roles; each may maintain a small component of the other (for example, the FBI Police). The agencies have nationwide jurisdiction for enforcement of federal law . All federal agencies are limited by the U.S. Code to investigating only matters that are explicitly within the power of the federal government . However, federal investigative powers have become very broad in practice, especially since the passage of the USA PATRIOT Act . </P> <P> The Department of Justice (DOJ) is responsible for most law enforcement duties at the federal level . It includes the Federal Bureau of Investigation (FBI), the Drug Enforcement Administration (DEA), the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), the United States Marshals Service, the Federal Bureau of Prisons (BOP) and others . </P> <P> The Department of Homeland Security (DHS) is another branch with numerous federal law enforcement agencies reporting to it . U.S. Customs and Border Protection (CBP), U.S. Immigration and Customs Enforcement (ICE), Federal Air Marshal Service (FAMS), United States Secret Service (USSS), United States Coast Guard (USCG), Homeland Security Investigations (HSI), and the Transportation Security Administration (TSA) are some of the agencies that report to DHS . It should be noted that the United States Coast Guard is assigned to the United States Department of Defense in the event of war . </P>

Who has the most authority in the usa