In this country, the citizens have guns too. This is actually a pretty big reason for why the police are so heavily militarized here as compared to gun-prohibitionist nations like France or Germany.

But the law does not boil down to men with guns--it boils down to our voluntary consent to live by the laws by choosing to live here (immigrants) or to remain here (everyone else) as opposed to somewhere else, like the wonderfully law-free nation of Somalia.