That's kind of a strange statement. "Legal" but restricted to military, police and licensed dealers is pretty well defined as ILLEGAL to anyone except maybe lawyers.
Not strange at all. State law can prohibit the possession or use of any firearm by anyone in the state, including the police military and licensed dealers. Until recently it was a felony in MN for a licensed dealer to possess a silencer, the police had to get them from out of state. Even now it is illegal for the MN police to use a silencer for anything other than emergency tactical response. This rules out their use in training by the police in MN. Until July 2011 it was a gross misdemeanor for anyone (military and police included) in WA to use a silencer on a firearm.
The requirements for silencer possession and use by the police, military and dealers vary from state to state; but in every state they are now legal for these organizations to possess them.