Domestic Climate Litigation: Discretion of States in Defining Emission Reduction Targets

In 2022 and 2023, requests for advisory opinions were submitted to the International Tribunal for the Law of the Sea, the International Court of Justice and the Inter-American Court of Human Rights asking the judges to clarify the obligations of States under international law to protect the Earth’s climate system from anthropogenic greenhouse gas (GHG) emissions. Behind the at times verbose phrasing of the requests hides a basic question: Does international law require States to take more ambitious climate action than what the Paris Agreement and the nationally determined contributions (NDCs) submitted thus far provide for? Several domestic courts have had a chance to answer a similar question under municipal law. Among them, the Dutch courts gained worldwide prominence for ordering the State of the Netherlands to reduce the country’s total GHG emissions by the end of 2020 to at least 25 % below the 1990 level and the country’s then-largest corporation, Royal Dutch Shell, to cut its total CO2 emissions across scopes1 to 3 by the end of 2030 to at least 45 % below the 2019 level. IPCC reports (in particular, AR4, AR5 and SR15) and estimates of required emission reductions contained therein have been central to both arguments put forward by claimants and the reasoning by the domestic courts across jurisdictions. However, while the courts agree on the urgency of the climate challenge, they differ in conclusions as to the States’ ensuing legal obligations. The judgements of the Dutch courts which borrowed verbatim the reduction figures from the IPCC reports are rather an exception than the rule. This article reviews the different approaches to interpreting States’ climate mitigation obligations by contrasting the reasoning of the Dutch courts with that of the other domestic courts which were faced with similar claims — in particular, the Constitutional Court of Germany, the Tribunal of First Instance of Brussels and the Court of Appeal of Brussels (Belgium), among others. Some thoughts are offered on the range of interpretive choices that international courts and tribunals are likely to face in the pending advisory proceedings in the light of this domestic litigation background.

climate change, IPCC, UNFCCC, Paris Agreement, GHG emission reduction, climate mitigation, due diligence