We could be like the Roman Republic, and rely solely on precedent and whatnot.
Or, you know, like the United Kingdom, which is the same way.
Not a system I would rather like to emulate, given the tendency of politicians through the ages towards incredible abuses of power.
Correct me if I'm wrong, but the United Kingdom hasn't had an autocratic regime since roughly one hundred years before our Constitution was written.
And, of course, there have been no notable abuses of power in the US since the adoption of the Constitution.
