Does the U.S. Department of Justice have the legal authority to investigate municipal police departments?

The U.S. Department of Justice has the legal authority to investigate municipal police departments under the Violent Crime Control and Law Enforcement Act of 1994, the Omnibus Crime Control and Safe Streets Act of 1968 and under Title VI of the Civil Rights Act of 1964 when agencies receive federal funding. 

These laws grant DOJ permission to review practices of non-federal law enforcement agencies that may be in violation of citizens’ federal rights. Reviews are often prompted by reports that indicate a pattern of violations or bias. 

The DOJ is a part of the executive branch, but follows guidelines that dictate independence in decision-making on matters of criminal and civil law enforcement. Personnel responsible for initiating and supervising specific cases, like local police investigations, do not communicate with the White House regarding such decisions, per department policy.