In addition, there is uncertainty about WTO compatibility in distinguishing a product based on the way that product is produced, rather than on the final product’s characteristics. There is also controversy over whether WTO jurisprudence has moved beyond the PPM concept (Zhang, 2004, Zhang and Assungao, 2004, Howse and Van Bork, 2006). Thus a negative approach will not work in a post-2012 climate regime.