I would suggest that a reasonable threshold test of the seriousness of a given individual's avowed theory of constitutional interpretation is whether the theory produces any results to which the individual finds highly objectionable. If not, there may be reason to suspect that the theory is just a dressed up iteration of the individual's policy preferences.
In other words, your constitutional theory has to produce results you don't like: laws you hate being upheld, and laws you like being struck down.
That certainly sounds right. We don't want judges just striking down laws they disagree with, and upholding those they like. We might suspect that that is what is going on, but we don't like it. Indeed, the whole impetus for a constitutional theory is to somehow constrain judicial subjectivity, to allow constitutional law to escape the taint that it is just politics done by people in Santa Claus suits.
It isn't hard, in fact, to find constitutional positions which differ from the policy position the judge or the professor would prefer, but only with a naive view of what the policy issue is. Once we define the issue in the way a constitutional lawyer is likely to, then the gaps become trivial (and rightly so). Franck's examples of positions he is reluctantly forced to take by the constitution are actually bogus: given a wide enough view of the facts, he wouldn't really prefer those results after all.
Let me illustrate by way of anecdote. I recall a Question-and-Answer session with Justice Scalia of the US Supreme Court at law school a decade ago. He was arguing that his "faint hearted originalism" avoided judicial subjectivity. Someone asked him the obvious question of which decisions he had made that went against his view of how things should be. As a response, he gave the flag burning case, in which he had joined the decision that statutes banning desecration of US flags were unconstitutional. As a patriotic sort, Scalia said, he hated flag burning, but as a strict constitutionalist, he had to invalidate the law.
Everyone in the generally-unsympathetic-but-polite crowd gave him a pass on that one. Generation X Torontonians love their flag, but have no desire to jail the grumpy vets who might want to desecrate the Pearson Pennant, so there was broad approval of Scalia's stand here. But, as so often happens in real litigation, I got to thinking of a response after the event. Scalia hadn't necessarily given an example of a policy result of which he disapproved. No doubt he dislikes flag burning, but even on a policy level that would hardly be enough. The policy question is whether he thinks banning flags would do more harm than good, given America's commitment to free speech. And he undoubtedly would answer that question with a "yes". He'd still ban some speech, after all: I imagine laws against hiring contract killers would still be OK in Scalia's America.
Scalia would uphold an increase in the federal minimum wage, even though he disagreed with it. But that's not because the constitution made him do it: on the contrary, there is a perfectly sound argument that such a thing would extend beyond the boundaries of the Commerce Clause and offend the Fifth Amendment. He'd do so because he thinks the courts would do more harm than good if they got involved in economic matters -- a policy question, albeit one at a higher level of abstraction.
And the policy questions are at a higher level of abstraction on the other side too. David Souter voted as he did in upholding the expropriation of Mrs. Kelo's property not because he was profoundly supportive of New London's redevelopment scheme, but because he doesn't want the courts determining what "public use" is. That's a perfectly defensible institutional point: the courts are likely to be a lot worse and less legitimate when doing that than they would be in figuring out what "just compensation" amounts to. But greater deference to government on one phrase than another in the same clause in the constitution is surely justified -- if at all -- by the likely effects.
In Canadian jurisprudence -- especially before the Charter -- it was often said that the courts were uninterested in the wisdom of the legislation in determining whether it was rightly enacted by the federal or provincial legislature. Rightly so, but they should not have been (and weren't) uninterested in the wisdom of who to leave the issue with. It's easy to look at the words of the constitution and figure out that lighthouses are federal, but on more important issues, the question comes down to institutional policy.
So "Adler's axiom" only applies to those aspects of the constitution set out in specific detail: everyone has to agree that the US Constitution requires the President to be 35 and the Canadian constitution requires that PEI get four senators, regardless of whether either rule is a good idea. The provisions that generate litigation are the ones (almost) everyone agrees with because they are so vague ("equal protection", due process, principles of fundamental justice, free speech, yada, yada). Everyone likes them because for everyone they apply as the applier thinks a constitution should apply. If you are pro-life and don't think the democracy should override your principles, then "life, liberty and security of the person" means the fetus's life. If you are pro-choice and think likewise about majoritarianism, it means a woman's liberty to terminate a pregnancy and her security from an unwanted one. If you think Parliament should decide, then its decision is consistent with fundamental justice. No matter what, the constitution says what you prefer, because that was what it was designed to do.