doesn't say you can't. the founding documents are a presumption of liberty for the people. whatever they choose to do, as long as it hurts no one. the constitution was designed specifically to reign in the government, not the people.
but, i have to agree with the OP. it is in the natural and unalienable right of self protection from tyranny that the fight lies.
the existence of the constitution and the bill of rights help tremendously, though. because the ideas of liberty have been codified, in a sense. and they're not going away any time soon.