Rich Ulmen
Former 13 Yrs as Agent Partially as a Deputy Marshal1y
The US Marshal and his deputies have more authority than any other federal law enforcement officers. U.S. Marshals can enforce all federal law and all state laws. However, the DOJ and 18USC have assigned primary investigative authority for many crimes to the FBI. Title 21USC is mostly enforced by the DEA. But FBI and DEA task forces ask to swear in their local police members as Deputy US Marshals for the above reasons. A good rule of thumb is the FBI is an investigative agency (a very political one lately) and the US Marshals are an enforcement agency. The US Marshals also investigate child trafficking and child molester cases and escape from federal custody and assaults of federal officers and related probation parole and other crimes. Additionally, most areas have a US Marshals led violent crime and drug trafficker fugitive task force.
The US Marshall Service is also assigned to protect federal judges and courthouses, and yet very few people were arrested for attacking federal court houses during the BL riots.