At NRO, Ed Whelan has a four-part review of Randy Barnett's Our Republican Constitution (Broadside Books 2016). Here are part 1, part 2, part 3 and part 4.
Parts 3 and 4 are, I think, the most important, and illustrate the two core differences between libertarian orignialism and more conventional originalism. First, from part 3:
Barnett particularly criticizes the “Thayerian” version of “judicial restraint” or “judicial deference,” and the readers of his book might well be left with the impression that the only viable alternative is Barnett’s “judicial engagement.” Such an impression would be mistaken.
In an 1893 law-review article, Harvard law professor James Bradley Thayer adopted an extreme view of deference under which a federal court should not strike down a federal law merely because it “conclude[s] that upon a just and true construction the law is unconstitutional”; rather, it should do so only “when those who have the right to make laws have not merely made a mistake, but have made a very clear one—so clear that it is not open to rational question.”
As I have observed before, among the many originalist proponents of judicial restraint, there might be one Thayerian. ... As law professor John McGinnis has explained in “The Duty of Clarity,” there is ample middle ground between Thayerian deference and no deference. Specifically, McGinnis makes the originalist case for a more modest “deference theory” that “requires the judiciary to decline to displace legislation unless it conflicts with a meaning of the Constitution that can be clearly ascertained after applying all legal methods.”
The amount of judicial deference owed to the political branches is a major point of disagreement among originalists. I agree that it is a spectrum rather than a dichotomy. But I would add that the McGinnis model is not necessarily the preferred model, even among conventional originalists. For example, I wouldn't say that Justice Scalia (for all his exalting of democratic values) was deferential in applying actual provisions of the Constitution (as opposed to propositions he regarded as invented by judges). For example, he voted in favor of the constitutional challenge to Obamacare, where more deferential originalist judges such as Jeffrey Sutton and Laurence Silberman voted the other way.
Next, from Part 4:
Barnett contends that the[ ] Due Process guarantees mean that any person subject to a law that restricts his life, liberty, or property must have a “fair opportunity to contest whether [that law] is within the ‘proper’ or ‘just power’ of a legislature to enact and therefore carries the obligation of a law.” (P. 228 (emphasis in original).) A law that is “irrational or arbitrary” is by definition “not within the just powers” of a legislature—even if it is enacted through an exercise of a constitutional power. (P. 228.) Further, if a power is being exercised for a just purpose, “we must next ask if the restriction of liberty is necessary to serve” that purpose. “Strict logical necessity is not required,” but “some degree of means-ends fit must be shown.” (P. 231.)
My basic question for Barnett is: Where does all this come from? How, in particular, does it flow from the original-meaning principles that he advocates?
Even more than judicial deference, I think this is the fault line between libertarian originalists and conventional originalists. While sometimes mis-described as a question of deference, it's really a question of substance: does the due process clause give judges the ability to assess the substantive rationality of a law? (Scalia, representing conventional originalism, thought no -- even though he was, as noted, not especially deferential in applying other constitutional provisions). Even here, though, there may be a spectrum of views. See this post from yesterday.