The PPM issue has been one of the most debated topics in the trade and environment debate. Even though the US–Shrimp case showed that PPM measures are not prohibited per se under the GATT, many questions remain unanswered when it comes to the precise conditions under which environmental PPM measures are justifiable under WTO law, for example in the field of trade measures relating to climate change mitigation efforts, natural resources management policies and biodiversity conservation measures.