To protect and defend

In discussing the oath the Constitution calls on each president to make upon taking office, Amar in his book "America's Constitution: A Biography" makes the point that the President swears to defend the Constitution itself, as opposed to the laws passed by the Legislature, as did the king of England upon taking throne. "In England, Parliament's enactments were supreme positive law, and a law-abiding monarch thus had to pledge allegiance to them. Such was the bedrock principle of the Glorious Revolution. In America, the bedrock principle was not legislative supremacy but popular sovereignty. The higher law of the Constitution might sometimes allow, and in very clear cases of congressional usurpation might even oblige, a president to stand firm against a congressional statute in order to defend the Constitution itself." (p. 179)