Now, why would someone submit as amicus curiae to the WTO? The incentive to submit is severely reduced by the fact that an amicus curiae brief (as explained in the Final Act) which contains factual information, if submitted to the Appellate Body, will be rejected. The factual record has to be established by the parties to the dispute and no one else at the panel level. This stems directly from the de-centralized character of enforcement of WTO obligations and the way Art. 17 DSU reads. A party to a dispute can decide though to incorporate in its submissions an amicus curiae brief. If the brief at hand contains factual elements, it must be incorporated at the panel level and it must be clear that the issue at hand had been previously discussed at the consultations stage. Otherwise, maybe even incorporation will not work. But if this were to be the case, why not send the information to the interested party right away instead of sending it to the WTO?
On the other hand, one would expect that a properly functioning democracy would anyway try to incorporate such views in its own brief. Hence only those briefs that somehow did not make it to a national submission and which do not extend to factual aspects of the case (as explained above) if presented as amicus curiae to the WTO have a chance to be reviewed.
These caveats notwithstanding, why would anyone send an amicus curiae brief to the WTO? Essentially for two reasons: to provide some information (an opinion how to interpret facts established by others) on the one hand, and to sensitise a court about the interest that a particular case might have for the wider public on the other. This second grounds is in fact the bridge between a court and the society.
Amicus curiae briefs hence represent an opportunity for any given court: to be exposed to an opinion and to see, through the submitted briefs, its role in the society within which it operates.
At the same though, amicus curiae briefs confer an advantage to the party to a dispute with which they side. Due process considerations can help ensure that there will be no undue advantage conferred to any party. After all, a court's role is to look for the truth (its truth, of course). The pleadings by the parties to a dispute circumscribe the dispute; they should not be understood as the frontiers of truth.
This is precisely why Art. 13 DSU exists: its function is to guarantee that panels will have the authority to look for answers beyond what has been pleaded. Such answers will of course be used to address a complaint as presented by the complaining party. In other words, one should not over-emphasize the de-centralized character of enforcement at the WTO. WTO Members are indeed the masters of their disputes only as far as their representation is concerned. From there onwards and all the way to the end result, there is only one master: the adjudicating body.
Art. 13 DSU is one avenue for WTO panels to honour their mandate. Due powers (the implicit powers as discussed in the Final Act) is the other. Amicus curiae are, as the term denotes, friends of the court. They are in principle committed to help the court in its search for truth. Public choice theory has helped us understand that we should always look at the incentive structure of the actor. And yes, many friends of the court are rather friends of themselves. They do not care about systemic issues, they do not care for the truth. They want to sell a message. But this is not an argument against accepting amicus curiae briefs. This is an argument in favour of selecting properly the members of a court.
On the other hand, probably the influence of amicus curiae has been grossly exaggerated: in a comprehensive study examining the influence of such briefs to the Supreme Court, Kearney and Merrill (2000) show that briefs by institutional litigants and experienced lawyers are those that have most of the impact. The first are anyway present in the WTO but as third parties whereas the second category has, to our knowledge, only been represented once in the WTO and the brief was rejected without motivation so far.9
Finally, the second grounds for submitting briefs cannot be over-emphasized when it comes to discussing amicus curiae briefs submitted to the WTO, an organization which has been accused (and continues to be) non-transparent, undemocratic, non-representative of modern concerns. Opening up the door to non-institutional players is probably the best way for the WTO to explain itself against a series of (most of them, completely unwarranted) accusations. But more on this later.
9 Robert Howse submitted an amicus curiae in the Asbestos case. His brief was rejected, along with the other briefs submitted, without motivation.