The United States Marshals Service (USMS) is a federal law enforcement agency within the United States Department of Justice (see 28 U.S.C. ยง 561) and is the oldest federal law enforcement agency in the United States. The U.S. Marshals Service holds the broadest authority of all federal law enforcement agencies. The official spelling is the plural form "US Marshals Service", not the possessive form "US Marshals' Service."
The USMS is the enforcement arm of the federal courts, protecting federal courts and ensuring the effective operation of the judicial system.