by Duncan Hollis
First of all, I need to say thank you to all the contributors to the current symposium on my book, The Oxford Guide to Treaties. It's quite common in academic circles to have symposia on "affairs of the day" (and, to be clear, those affairs often trigger very important issues like targeted killing, cyberwar, climate change, the EU fiscal crisis, etc.). But, I think it's equally important to step back from time to time and have conversations about the international legal system itself, of which treaty law and practice now forms a large part. Thus, I've greatly appreciated the discussions over the last several days on whether reservations can be severed, the rule(s) of treaty interpretation, the increasing "publicness" of treaty functions, and the role of non-State actors in modern treaty-making.
In reading these posts, moreover, I was struck by how some of them suggest (albeit implicitly) a new way to think about the fragmentation of international law. To date, we have tended to think about fragmentation in one of two ways. First, we have the question of "normative" fragmentation, where two rules produced by different legal regimes conflict or compete with each other, meaning that a State has to choose to which rule to give priority. We normally talk about this as the "trade and . . ." problem where WTO rules have been said to conflict with rules of international environmental law, international labour law, etc. But, normative fragmentation is not limited to the trade context as witnessed by the question of what to do when UN Security Council resolutions on international peace and security conflict with EU Law in the Kadi case. Second, fragmentation may also arise where the conflict is not between the rules but who applies them; that is, competition or conflict over which tribunal or court should be authorized to have the final say on which rules apply or what a particular rule means in a given situation. The MoX case is a paradigmatic example of this inter-tribunal competition, with three different proceedings under three different normative regimes: an arbitral tribunal pursuant to the 1982 U.N. Convention on the Law of the Sea, dispute settlement under the Convention on the Protection of the Marine Environment of the North-East Atlantic, and proceedings before the European Court of Justice pursuant to the European Community and EURATOM treaties.
As I think about the law of treaties, however, I see the potential for a third type of fragmentation within international law, or what I'll call "secondary" fragmentation. My basic idea is that fragmentation is not limited to competition and conflict among primary rules, but can also occur with secondary rules. Here, I'm employing H.L.A. Hart's famous division of rules into primary and secondary categories. Primary rules are rules of conduct -- telling States and other subjects of international law what they are obligated to do (or not do). Secondary rules, in contrast, are "rules on rules", or rules that tell us how to form, interpret, amend, or extinguish primary rules. When we talk about normative fragmentation, however, almost all the existing discussion has emphasized conflicts and competition among primary rules, e.g., should a WTO rule trump or defer to an international environmental rule?
In looking at the various posts on interpretation and Geir Ulfstein's post on treaty functions, however, it seems there's some evidence of a different kind of fragmentation emerging among the secondary rules of international law. For example, Geir suggests at the end of his post that "Treaty law must be complemented by international institutional law". But treaty law and international institutional law are not required by any rule of international law to get along -- it's equally possible that the result produced by the law of treaties (say an interpretation of a treaty constituting an International Organization under VCLT Article 31) and international institutional law (say an interpretation of the same treaty employing the implied powers doctrine) could generate competing or conflicting results with respect to the same primary rule. Catherine's post makes this point more descriptively, noting how international institutional law has come to supplant the general law of treaties in the IO treaty context. As with fragmentation among tribunals or primary rules, however, international law doesn't tell us if this is the correct result. Examples of secondary rules that are conciliatory to other secondary rules are relatively rare -- although the VCLT does include a few examples with respect to IO treaties in Articles 5 and 20(3). But, on the whole, the international legal order says little, if anything about whether one set of secondary rules should be accorded priority over another.
Moreover, I don't think this competition over interpretative rules is an isolated case. Although The Oxford Guide to Treaties does not explicitly flag this idea of secondary fragmentation specifically, there is evidence of it in several other chapters. For example, although the VCLT's rules on material breach purport to function differently than the law of state responsibility, Bruno Simma and Christian Tams' chapter on remedies for treaty breach makes clear that these two sets of "secondary" rules are in competition with one another (and, moreover, that the law of state responsibility on countermeasures may be winning in the sense that it is those rules not the VCLT provisions on which States currently rely). Malgosia Fitzmaurice's chapter makes a similar point about tensions over exceptional circumstances where the law of treaties has doctrines -- impossibility, and rebus sic stantibus -- that may be threatened by the law of state responsibility's doctrine of necessity.