The burden-of-pleading rule defines “the set of issues that each party must assert in order to put those issues into play.”225 That is, unless the party who bears the burden of pleading for an issue asserts the availability of the issue in the case, the court does not have to examine the issue. In most cases, the party who bears the burden of proof about an issue has to bear the burden of pleading about the issue.226 However, that is not always the case. For example, under U.S. tort law, although defendants must plead contributory negligence, some states impose the burden of proof on plaintiffs.227 According to Lee, the “divergence” of allocation between the pleading of proof and the burden of proof can be economically justified. Lee maintains that the burden-of-pleading rule functions as a device for reducing process costs in two ways. First, process costs could be saved by placing the burden of pleading to defendants about those issues which are unlikely to arise. Otherwise, process costs increase since plaintiffs have to raise every possible issue including the ones which arise infrequently. Second, through imposing the burden of pleading on the party to whose “version of the issue in question is more discrete”, the process costs could be saved.228 By so doing, the other party does not have to anticipate and produce evidence contravening the indefinite number of possible claims and arguments.229 For example, in the context of contributory negligence in the U.S. tort law, the allegations of defendants would be more “focused” on certain elements of the case than the allegations of plaintiffs. In other words, if plaintiffs have to bear the burden of pleading, they have to assert that they were not negligent in all the aspects of their behavior in the case. Therefore, the burden of pleading is imposed on defendants in the context of the U.S. tort law. However, because plaintiffs have better access to the information with regard to the level of care of themselves at the time that the case (for example, a traffic accident) occurred, some courts impose the burden of proof on plaintiffs.230 In sum, since the burden-of-proof and burden-of-pleading rules reduce process and error costs in different ways, allocating burdens to different parties under burden-of-proof and burden-of-pleading rules could be justified.
In the context of the WTO, the AB&P have seemed to be aware of the issue of the divergence between burden-of-proof and burden-of-pleading rules. For example, in Asbestos, in applying the LTRA test and the chapeau test, the Panel seemed to allocate the burden of pleading to Canada, the complaining country, even though the Panel clearly pronounced that the EC, the respondent, bore the burden of proof. That is, in applying the LTRA test in its GATT Article XX (b) analysis, the Panel only examined the alternative courses of action which were asserted by Canada in spite of the possible availability of other alternatives. Furthermore, in its chapeau analysis, the Panel found that the application of the French measure did not result in “unjustifiable discrimination”, “arbitrary discrimination”, or “disguised restrictions on trade” since Canada did not argue that the application of the French measure amounted to according less favorable treatment to foreign products.231 These allocations of the burden of pleading under the LTRA test and the chapeau test make sense economically. In applying these tests, it is the complaining countries that can “narrow” the scope of their claims. If the AB&P impose on defending countries the burden of pleading, the defending countries would have to anticipate all possible claims and produce evidence refuting all of them. The AB&P would also have to examine all the points. On the other hand, if the burden of pleading is imposed on the complaining countries, the defending countries merely have to refute the arguments made by the complainants; in addition, the issues which the AB&P have to examine are also limited to these points. In sum, process costs can be saved by imposing the burden of pleading onto the plaintiffs. On the other hand, as we discussed above, the burden of proof should be assigned to defending countries in the context of GATT Article XX analysis since it is unlikely that the arguments of the defending countries are meritorious and the costs of obtaining evidence regarding the issue involving GATT Article XX by defending countries would be less than those of the complaining countries. In this way, allocating the burden-of-proof and the burden-of-pleading on different parties could be justified in the context of GATT Article XX analysis.