(1) In Restoring, I begin by denying that the legitimacy of a constitution of the sort that governs a territory like the United States could ever be grounded on the "consent of the governed" because such consent is and must always be a fiction. If such a constitution is ever legitimate at all (and perhaps none can be), it must be because it is warranted in imposing its commands on nonconsenting members of the public.
It's funny how much of his later argument I find convincing, after totally rejecting this starting point. I don't believe that either consent or legitimacy are binary values.
No government is totally consensual or non-consensual, no government is totally legitimate or illegitimate.
Considering that the whole point of government is that it requires that you change your behavior, "the consent of the governed" is never 100%, but that doesn't make it a fiction: consent is not always additive because we consent to different things. Every government, even a thugocracy, is somewhat consensual. In the absence of Madison's angels, no real-world government can be fully consensual -- and if we had such angels as citizens, then Madison correctly points out that no government would be needed. A maximally legitimate government is one for which any change would make it even less legitimate -- less consensual -- than it is. Anarchy is pretty much the least consensual form of "government" for the simple reason that practically nobody consents to it; government by (consent of) "We the People" (via representatives picking metarules by which to pick rules) is necessarily far from perfect, but it's probably better -- more consensual -- than any of the alternatives.
And that's why we should pick it. (So am I ready to define "more consensual"? Absobloominglutelynot. I know it when I see it, except when I'm not sure, or when I'm wrong. But consent is weighted, in some sense: if you come up and hit me in the nose, to which you consent and I do not, then that's a whole lot less consensual than if the nice policeman stops you, to which I consent and you do not. If you claim that you don't believe this, I am skeptical about your disbelief.)
And yet Barnett goes on to derive presumptions of liberty and all kinds of good stuff which I also find to follow from my very different premises. This may indicate that I'm being convinced, and perhaps even that he's being convinced, by something other than the ostensible basis of argument.
Or then again, maybe not.
update: Barnett now points to Solum on Leiter (and Me) on Originalism:
The truth of semantic originalism, by itself, has no normative implications. Even if the semantic content of the constitution is the original public meaning, it could be the case that constitutional practice should deviate from that meaning. For example, one might argue that precedent should trump the original public meaning. Or one might argue that the difficulty of constitutional amendment so undermines the democratic legitimacy of the Constitution that the political branches are justified in “amending constructions” that give the text new and different semantic content. Or one might believe that the constitution is so undesirable or unjust ...
As a simple-minded geek, I think that Solum is using the same oversimplification that Barnett does: I would say that semantic originalism (original public meaning) has no normative implications in a predicate-calculus prove-true-or-false sense, but that it has normative weight in that the original public meaning is what was agreed/consented to at the time, and times, of the agreement and its subsequent amendments. That's where consensuality comes in. Other issues (including justice, not always separate from consensuality) come in too, of course. I would like to disagree with Solum (and Barnett, I think) about constitutional underspecification, especially vagueness, in that if the original public meaning is vague, then surely (I wish) it does not constrain, so anything goes within the range of vagueness. Unfortunately, I can't do that, because the clear non-vague original public meaning of the 9th Amendment says that there are "rights" -- constraints on Congress -- as a part of this stuff that we're consenting to, that are not enumerated. The resolution of this underspecification in particular, and perhaps vagueness-underspecification as well, is clearly not being left to Congress and presumably not to the Executive either; it's gotta be a judicial function. I really don't like that, but maybe it was the best available option and, gee, what can I say? It's what they consented to, and I have no clarifying amendments to suggest.