A legal standard for state mitigation efforts: is national discretion bound to shrink over time?

Every five years, parties to the Paris Agreement are obliged to communicate a new greenhouse-gas-emission mitigation target known as a Nationally Determined Contribution (NDC). These targets are not legally binding, and states retain significant discretion over their level of mitigation effort. This raises the question whether the Agreement contains a standard (binding or not) applicable to the substance of NDC targets. In this chapter, I identify a ‘bundle’ of provisions that, taken together, grant parties considerable discretion in choosing their targets and implementation measures. Yet, I also argue that the Agreement’s mitigation standard has the potential to become increasingly stringent each time parties complete a new cycle of target-setting and international accountability. I offer examples of NDC communications, domestic laws and policies, and climate-litigation cases that suggest that national discretion under the Agreement has already begun to shrink. Further research into this dynamic area of international climate law is called for.