Going Beyond Non-Discrimination

From a speech by WTO DG Pascal Lamy:

Growing  interdependence among nations, as well as growing consumer awareness, have  certainly focused greater attention on NTMs [non-tariff measures]. As the use of NTMs increases, the  potential for friction is likely to increase. A number of high-profile disputes  have already arisen around public policy measures. The SPS and TBT agreements  go beyond non-discrimination and include the need to ensure that measures are not  unnecessarily trade restrictive. As has been made clear by recent decisions of  the Appellate Body, this can involve WTO adjudicators being called upon to assess  the legitimacy of the objectives that a member pursues through domestic  regulation, and to scrutinize the regulatory choices and distinctions that it  makes in seeking to achieve those objectives.  Some question the appropriateness of  adjudicators having to do this, and ask, more generally, how the line should be  drawn between an inappropriate inquiry into government motivation and an  appropriate assessment of measures that have trade effects and that are  challenged by other members.

I'm a little puzzled by this last sentence.  Why is an "inquiry into government motivation" called "inappropriate" and an "assessment of measures that have trade effects" called "appropriate"?  Or am I reading this wrong?  There is little doubt that both "motivation" and "effects" can be controversial and sensitive issues, and we need to think carefully about how this analysis should be carried out.  To me, though, the main source of the problem is where the rules prohibit measures due to their "trade effects" in situations where the measures affect both domestic and foreign products/producers equally.