where a bilateral investment treaty bit or multilateral treaties such as the world trade organization wto trade rules or the north american free trade agreement nafta protect foreign investors from expropriations they may seek claims in response to climaterelated law and policy although this has not yet happened with respect to domestic climate laws it has occurred with respect to other environmental laws despite the exemptions for environmental policy in most trade agreements including the general agreement on tariffs and trade of gatt article xx these rules limit the ability of states to impose regulations of an internationally traded good on the basis of the process and production method ppm used to manufacture such good this issue has already seen a challenge directly bearing on a countrys ability to implement their ndcs