States’ current emission policies are far from being aligned with what is needed to meet the Paris Agreement’s temperature goal. Against this backdrop, an increasing number of lawsuits have been filed around the world. As of March 2024, most courts have exercised restraint in imposing substantive limits on the legislator’s discretion in determining emission levels. Judicial restraint commonly rests on two premises: Climate models yield wide uncertainty ranges and choosing emission reduction levels is a normative decision belonging to the political domain. By engaging best available science on climate tipping points, this article examines the reasoning in favour of political discretion through a due diligence and equity lens. The analysis concludes that all factual requirements are met for states to be under an obligation to align their mitigation policies with a global carbon budget which is expected to limit global warming to 1.5°C at a likelihood as high as state capacities allow for.
