My answer to Orin is that “law” can validly mean many things, depending on the context and what you want to use it for.
For instance, Holmes — explaining his famous “bad man” view of the law — says that law is “the prophecies of what the courts will do in fact.” (See The Path of the Law, 10 Harv. L. Rev. 457, 461 (1897).) We can expand this a bit beyond courts and say, with Eskridge and Frickey, that “law is a prediction of the rules that interacting government institutions will apply.” (See Law as Equilibrium, 108 Harv. L. Rev. 26, 77 (1994).)
Thus, in most of our lives, most of us don’t care what the law is in any abstract sense (I sure don’t!); we just want to know what we should or shouldn’t do if we want to avoid being punished by someone. That, to us, most of the time, is Law. Constitutional law is just a subset of law, so, among other things, we might want to know what we should or shouldn’t do if we want to avoid being unconstitutional, which will usually be relevant only if we’re some government actor. (But see Amend. 13, which means any private slaveholder is acting unconstitutionally!)
So usually, constitutional law will be current Supreme Court doctrine. It’s possible that other branches might be applying their own constitutional rules — maybe the Executive Branch has a policy of withholding government funds from property development projects it believes are unconstitutional, and maybe it has a different view of the Takings Clause than Kelo — so then, from your perspective, constitutional law would also consist of the views of those other branches.
But that’s not the only view of law! For instance, there are all sorts of unenforced or underenforced constitutional commands. The Suspension Clause says the writ of habeas corpus won’t be suspended, unless in case of rebellion or invasion the public safety requires it. If Congress suspends the writ, it’s unlikely that the Supreme Court would ever judge whether the public safety really requires it, or whether what’s going on is really a “rebellion.” There are lots of political questions like that, and other “underenforced constitutional norms.” It’s not that there’s no law to apply — it’s just that whatever law there is is unenforceable.
Does that mean there’s no law? From the “bad man” perspective above, that is correct — there’s no law. Congress can suspend habeas even when there’s no rebellion or invasion or the public safety doesn’t require it. But suppose — just suppose — that for whatever reason, you wanted to follow constitutional commands, perhaps because you took an oath to that effect and want to live up to it. In that case, the Constitution becomes an independent source of duties for you, and you have the obligation to figure out what duties it imposes.
Now you could just decide to listen to the Supreme Court all the time, or on certain questions (perhaps whenever there’s something enforceable), or whatever; but that will be your choice. There’s nothing in the Constitution that says the Supreme Court is always right. If you have a view on how the Constitution should be interpreted, and, after due consideration, you decide that you disagree with the Supreme Court, why not follow your own view? (Especially, as I said in my previous post, if the Supreme Court won’t stop you, for instance if you take a more protective view, not as a matter of policy but as a matter of constitutional meaning.)
So suppose you decide that you believe in original public meaning. And you observe that, low and behold (moo!), all these originalist textualists have already created a whole body of work explicating that meaning! No need to read those pesky Supreme Court opinions (except for prudential reasons, to the extent they’d actually frustrate your plan); you’ve already got a whole set of binding principles that tell you how to act. What are these principles if not law?
Well, you don’t have to call them law, but from your perspective, they’re as binding on you — if unenforceable by judicial means — nay, more binding on you!, than the stuff laid down in Supreme Court opinions. It’s what the “bad man with a conscience” has to follow if he doesn’t want to be punished by his conscience. No, I don’t think that all moral rules that you feel are binding should be called “law” — if you were elected to office wanting to implement Kantian ethics, that wouldn’t be law. But I do think it’s fair to call them “law,” at a minimum, if they derive from what are commonly recognized as legal principles, for instance, interpretation of a legal document. Once what you’re doing purports to derive from a statute or constitution or treaty or suchlike, the rules that you derive that you claim bind you and should bind others are properly called “law.”
Yes, this means that Hectorism can be considered “law,” and arguments deriving from Hectorism are “legal arguments.” It doesn’t mean that non-Hectorists should give it any consideration, because, life being short, it’s only worthwhile considering theories that (1) are actually applied in the world by at least some people, OR (2) are actually advocated in the world by people you respect, OR (3) are, in your view, meritorious.
And, as a final note: These arguments don’t need to be OUGHT arguments at all. I’m perfectly capable of arguing that “the original public meaning of the Second Amendment implies position X,” even if I don’t believe that original public meaning has any normative value at all. It’s just fun to talk about it! Larry Solum’s recent article on Semantic Originalism, if I understand it correctly, makes the point that the meaning of the Constitution is original public meaning, but separates that from the question of whether one should actually follow the meaning of the Constitution.
So a non-originalist can make arguments from original public meaning that are contrary to Supreme Court doctrine; those can definitely be IS arguments about the meaning of the Constitution without being OUGHT arguments. And of course one can make OUGHT arguments without making any legal IS arguments about anything. For instance, “We should adopt position X because it’s required by Kantian ethics” is an OUGHT argument, and is also an IS argument about Kantian ethics, but is not a legal IS argument.