Require all civilian law enforcement agencies (which includes but is not limited to the FBI, Secret Service, state, and local law enforcement agencies) to abide by federal, state, and local firearms laws (which includes but is not limited to the 1934 National Firearms Act, the Gun Control Act of 1968, the closing of the machine gun registry in 1986, state laws, and local laws concerning so-called "assault weapon bans", magazine restrictions, concealed carry, etc.) Since the above mentioned agencies are civilian agencies, they should not be exempt from civilian laws pertaining to firearms.
If these weapons are only used for mass murder, why do the police need them?