"I do solemnly swear (or affirm) that I will... protect and defend the Constitution of the United States."
No, not the piece of paper; what it SAYS. Regarding what it says, my paper "Action-Based Jurisprudence" (2011) included the following one-footnote book review (p. 35, fn 31):
"[Randy E. Barnett, in Restoring the Lost Constitution: The Presumption of Liberty (Princeton: Princeton University Press, 2004)] argues that the US constitution’s actual conception of rights is essentially a libertarian one. He forwards an “original meaning” standard, which uses documentary evidence to establish what the language of the final enacted text meant in view of linguistic usage at the time. He contrasts this with “original intent” attempts to speculate as to what “the Framers” may have wanted to accomplish with the text. He argues that the restrictions and limitations in the document are placed on the powers of the federal government and not on the rights of the people and states it was designated to serve. The entire structure creates a “presumption of liberty” for the people in any area of dispute with the federal government.
"While he makes a compelling case for respecting what the Constitution says so long as it remains notionally in force, I find this line of argument weak if it is be viewed as a reform pathway. This is because, precisely as Barnett shows, the original document already made its own meaning perfectly clear. Yet despite this clarity, post-enactment history has still been a story of powers expanding and rights being limited in direct contravention of the unmistakable meaning of the enacted text. We should not expect the underlying factors behind this process to change based on another, even clearer presentation of the plain meaning of the enacted text, such as Barnett’s. The problem is that any state placed in charge of judging the extent of its own powers will surely manage to wear down, redirect and overcome such efforts at limiting itself, as the American experiment in substantive constitutional limitation so dramatically attests."
Barnett's own previous book, The Structure of Liberty: Justice and the Rule of Law (Oxford: Oxford University Press, 1998), makes substantial contributions toward understanding why a written constitution should in all cases fail to actually limit the activities of a monopolistic government indefinitely. Both books are insightful and worth reading, and the latter effort makes the original-meaning case well. However, the earlier book seems to be the more realistic one—by being the more radical one.