Further to Simon's post, I am not an EU law expert, but I do think that, in particular, the findings of the ECJ on proportionality are relevant to the WTO dispute. Here they are:
Second, the applicants’ argument that the basic regulation goes beyond what is necessary to achieve its objectives must also be rejected. The proportionate nature of that regulation cannot be examined in relation to objectives other than those pursued by that regulation.
94 The applicants’ argument that a labelling measure would be less restrictive and more effective for achieving the objectives of the basic regulation cannot succeed either.
95 It is apparent from the basic regulation that the adoption of a measure allowing the placing on the market of only such seal products as respect animal welfare requirements and, in particular, a labelling requirement were examined and rejected by the legislature. In that regard, recitals 11 and 12 in the preamble to that regulation state that ‘[a]lthough it might be possible to kill and skin seals in such a way as to avoid unnecessary pain, distress, fear or other forms of suffering, given the conditions in which seal hunting occurs, consistent verification and control of hunters’ compliance with animal welfare requirements is not feasible in practice or, at least, is very difficult to achieve in an effective way, as concluded by the European Food Safety Authority on 6 December 2007’ and that ‘[i]t is also clear that other forms of harmonised rules, such as labelling requirements, would not achieve the same result [and that a]dditionally, requiring manufacturers, distributors or retailers to label products that derive wholly or partially from seals would impose a significant burden on those economic operators, and would also be disproportionately costly in cases where seal products represent only a minor part of the product concerned[, whereas c]onversely, the measures contained in this Regulation will be easier to comply with, whilst also reassuring consumers’.
96 It must be concluded that, having analysed the question of the scope of such measures in practice, the legislature took the view that they did not allow the objective pursued to be met and that a general prohibition on the placing on the market of seal products was the best means of guaranteeing the free movement of goods. None of the arguments put forward by the applicants is capable of establishing that those findings are erroneous.