An important difference between legal interpretation and the interpretation of non-legal texts is that any legal interpretive methodology worth its salt needs to be capable of economical deployment by institutions that don’t have the time, budget or expertise to conduct deep, nuanced research and analysis. (A related, but less persuasive, consideration from democratic theory [as opposed to consequentialist theory] is that legal interpretation needs to be understandable by an “ordinary person” – this also limits the permissible extent of its nuance and depth.*)
From this distinction between legal and non-legal interpretation it follows that there’s no reason to think that general theories of interpretation give any indication of how to interpret the law.
First, they don’t indicate how judges actually ought to interpret the law because they are not built around the limitations that must be imposed on a viable theory of legal interpretation – unlike in the legal case, it is not a legitimate consideration in favor of a mode of scholarly exegesis that anything more thorough would have been too hard. They also don’t indicate how non-jurists ought to interpret the law because otherwise the meaning of “law-in-books” and “law-in-action” would differ even in a theoretically ideal world, licensing legal scholasticism.
Second, general theories of interpretation don’t indicate an ideal that judges should roughly approximate within their limited means. There is no reason to think that an approximately sound interpretive methodology is a preferable mode of doing business than some other mode altogether. For example, it might be that inept attempts to identify original meaning (assuming that’s the theoretically ideal goal) lead, because the interpreter is unconsciously in the grips of a tissue of biased anachronisms, to politicized holdings that could be avoided by settling e.g. for contemporary meaning.
There are various presuppositions about legal interpretation implicated in the above that I do not buy. But most people do buy these presuppositions, and those who do should realize that the success of any argumentation about proper methodologies that doesn’t begin with an analysis of institutional capacity is a matter of sheer luck.
* Thomas Nagel flags this possibility in his article “Moral Conflict and Political Legitimacy” when, while unfolding his view that the state is only authorized to act when its conduct can be justified by reference to “common reason which is available to [even if not actually used by] everybody,” he observes in a footnote that this criterion might “exclude disagreements based on exceptionally subtle and difficult forms of reasoning…”.