Interpretation as the Continuation of Politics by Other Means
I would agree with Richard (and Isabelle) that not too much should be expected from any rules on interpretation. Interpretation is, so to speak, not entirely a rule-governed activity, in much the same way as playing the violin or the piano is not entirely rule-governed. Or building do-it-yourself bookshelves by following the manual, for that matter. I might be particularly clumsy in these matters (my wife would nod affirmatively if she would read this), but have the experience that trips to Ikea always end up in great frustration….
If this is plausible (and many seem to accept the proposition that interpretation is at least in part a matter of art and therewith of talent), then it would seem to follow that rules on interpretation can do little more than set the outward parameters: certain things are not acceptable to begin with. The strange thing now about articles 31 and 32 is that the one serious limit these rules set, is constantly ignored: I cannot think of a serious lawyer who would not at least have a look at some of the preparatory work to bolster her conclusion or, if necessary, reconsider her conclusion, regardless of whether an interpretation without the preparatory works would lead to ambiguous or absurd results. It is understandable that the drafters of the Vienna Convention felt the need to limit recourse to the preparatory works, if only for practical reasons (never mind that there are also good political reasons to limit recourse to the travaux): one would have a hard time figuring out relevant from not so relevant materials (plus debates, of course, on what exactly would constitute such relevant materials) and, more importantly still perhaps: it would lead to all sorts of difficult negotiations on what exactly the record should reflect. Imagine the sort of record created if the UNCLOS travaux would have been thought to be decisive for future interpretations; the process would in all likelihood have taken twice as long. Still, any lawyer worth her salt will consult whatever record is available.
The main function served by the Vienna Convention’s rules, then, is as something of a battlefield: the continuation of politics by other means. If you don’t get your way when drafting the treaty, you can still try to get your way when a particular provision or term comes to be applied, by trying to control the meaning assigned to it. And in order to be able to argue that something ought to be read in some particular manner rather than any competing manner, it proves convenient to have a rule to fall back, if only to suggest that you’re not just making a political or partisan point. It is this circumstance, I would guess, which gives articles 31 and 32 much of their salience, and which makes it attractive to invoke them. Isabelle hints at much the same when suggesting that the WTO panels initially felt the need to solidify their judicial function in the rough and tumble world of trade politics, and I’ll take her word for it that later panels (if not litigating parties, perhaps) have been able to relax their attitudes somewhat.
Whether that can be generalized or not is a different matter, perhaps. One factor militating against this is that even parties before the European Court of Justice, for all its self-containment, have seen fit to invoke articles 31 and 32 in recent years, and I don’t think the Court will have done much to tell parties otherwise. So perhaps the trend of the last 15 years, as Richard identifies it, is a bit more general indeed than merely the WTO trying to solidify its existence. But that raises another question: where does such a general tend stem from? What problem is it supposed to be a response to? Something to reflect upon…