From the Declaration of Independence. Not only do you have the right to overthrow your government, it is a responsibility placed on us by a founding fathers. If our government betrays us, acts other then in accordance to our wishes or we feel changes need to be made it is our obligation to do so.
"Whenever any form of government becomes destructive of these ends [i.e., securing inherent and inalienable rights, with powers derived from the consent of the governed], it is the right of the people to alter or abolish it, and to institute new government, laying its foundation on such principles, and organizing its powers in such form, as to them shall seem most likely to effect their safety and happiness." --Thomas Jefferson: Declaration of Independence, 1776. ME 1:29, Papers 1:315