The assumption of natural rights expressed in the Declaration of Independence can be summed up by the following proposition: “first comes rights, then comes government.” According to this view: (1) the rights of individuals do not originate with any government, but preexist its formation; (2) The protection of these rights is the first duty of government; and (3) Even after government is formed, these rights provide a standard by which its performance is measured and, in extreme cases, its systemic failure to protect rights -- or its systematice violation of rights -- can justify its alteration or abolition; (4) At least some of these rights are so fundamental that they are “inalienable,” meaning they are so intimately connected to one’s nature as a human being that they cannot be transferred to another even if one consents to do so. This is powerful stuff.
Really, read the whole thing. Great stuff. Via The Volokh Conspiracy » The Declaration of Independence Annotated.