A nation ruled by weapons 

will always be subject to them

It could be said that he who has the biggest gun sits upon the throne. If someone with a gun enters your life, they become your king. It does not matter if you have a president, or a state legislator, or a town mayor, at that moment the person with a gun stands before you, it is he who rules over you. So, a nation ruled by weapons will be subject to them. A nation of guns will be subject to them. You cannot allow a power greater than your own into your presence and expect that he will not rule over you.