The Invisible College
I am actually not sure whether it makes much sense, as Isabelle fleetingly suggests, to think of articles 31-32 in terms of either rules or principles. Following e.g. Rosenne, I tend to think that they lack any ‘norm-creative character’ (to use the phrase from the ICJ’s 1969 North Sea Continental Shelf cases), and are best seen as methodological devices: as instructions to whoever gets to be in a position to interpret a text. And methodological devices tend to be, so to speak, non-imperial: there are various different ways to engage in many activities, without it being possible to specify which one would be the best – this may well be why so many cookbooks are being produced…. Consequently, if it is not plausible to think of articles 31-32 as rules, it is not plausible to think of them as customary rules either (despite anything the ICJ may have said on the topic).
This does not mean that anything goes: interpretation is not an open-ended ‘free-for-all’. Typically, within the professional group of international lawyers, some arguments will be deemed more acceptable than others. Indeed, the same holds true within the sub-regimes, which may help explain why some in the human rights community were shocked (or mildly upset) by decisions such as the EC’s Court of First Instance decisions in Kadi and Yusuf a few years ago. The upset responses were not the result of the CFI somehow misapplying established rules of interpretation or applying the wrong rules of interpretation, but rather stemmed from the CFI’s unfamiliarity with human rights law. What may have made sense as a matter of EC law (one may have one’s doubts on this though), turned out to be less sensible from the viewpoint of the human rights community. The CFI ended up applying a body of rules without having acquired the sentivities of those who would normally be working with these rules, and as a result came up with readings of the right to property or access to justice that will not impress your average human rights lawyer.
By the same token, many in Europe at least have expressed some dismay at the US Supreme Court’s approach to consular cases, as highlighted by Duncan. These stem not so much (or not solely) from different methods of interpretation, but rather from the Supreme Court’s reluctance to adopt (or at least familiarize itself with) the sensitivities of international lawyers. This may be politically justified, perhaps; and it may be legally justifiable, perhaps, but those are different matters. As an explanation, the idea of there being different ‘invisible colleges’, in Schachter’s famous phrase, or different ‘interpretive communities’, as Stanley Fish puts it, seems to make some sense.
That also suggests that perhaps the most proper methodological device is that interpreters, judicial or otherwise, should show some humility and at least try to understand the mindset prevailing amongst the communities engaged in the body of law they are about to apply. An interesting exploration hereof is a recent study by H. Jefferson Powell with respect to the US Supreme Court (I forgot the title, and am not in a position to check right now). If one insists, one may see articles 31-32 as appeals to do just this, given their reliance on context, and the injunction to read in good faith.