politicians can't just change their tune contrary to a pulic vote here
They can just ignore the Constitution though, whenever they think it's "necessary". Bradley Manning didn't get a fair trial for example.
The all-encompassing surveillance kind of flies in the face of the Constitution too.
So basically, you're placing way too much faith in laws, which is of course exactly what they want you to do.
But in reality, the only limit on what rulers can do, is what the masses let them. Can they monitor everyone without getting overthrown by force? Then they'll do it.
Can they brutalize OWS protesters without getting overthrown? They'll do it.
Can their thugs arbitrarily confiscate people's property when they feel like it? They'll do it.
"Governance" is an euphemism for enslavement.