@engineer,
The weaponry in a drone is a laser/gps guidance system and a missile.
While on US soil I think it might be easier to simply pack that stuff into a utility vehicle and drive it somewhere near the target. You don't really need a million dollar drone unless you don't have ground access near the target.
So what you're really saying is that the Police should have access to military grade guidance systems and missiles.
They could also mount that type of weaponry onto one of their police helicopters. I don't really see a need for them to have unmanned drones for any of this.
So the problem really becomes just getting expensive military grade weapons systems like that into the hands of the police. Once they've got it the can handle it (in a strategic sense) just like a big gun and apply the same rules of engagement that they currently employ for their other big guns. I would think... Right?