The guns are for the possibility of civil war/social upheaval/violent revolt. At the end of the day, the rule of law is a thin veneer over the force of people with guns. (It is, to a first approximation, just a way of deciding who tells the people with guns what to do.)

To head off the inevitable "but a bunch of rednecks with guns would never be able to stand up to the military!" That's first-world myopia. Look at what happened when, e.g., Bangladesh became independent from Pakistan. A bunch of farmers did not take on the undivided Pakistani army. Instead, after initial skirmishes, part of the Pakistani army broke off and fought for independence alongside the revolutionaries.