If no criminals had guns, then the police wouldn’t really have much use for guns. They could use tazers against knives and the like, as they indeed do. It would be a much better world.
If your point is that only criminals would have guns… I have no idea where you’re going with this. Nobody’s proposing that law enforcement shouldn’t have access to firearms. If that’s what you’re arguing against, it’s the strawman to end all strawmen.