Climate change litigation in Europe has entered the realm of fundamental rights and constitutional law. The Supreme Court of the Netherlands (Hoge Raad der Nederlanden) has delivered an attention-grabbing judgment requiring the state to take substantive measures against climate change based on, inter alia, the European Convention for the Protection of Human Rights and Fundamental Freedoms. In Germany, the recently rendered decision of the German Federal Constitutional Court (Bundesverfassungsgericht) on the Federal Climate Protection Act (KSG) is also calling the state to honour its constitutional obligation to protect the life and health of its people against the effects of climate change, to limit global warming and to participate in related international efforts. The KSG judgment’s most characteristic feature, however, is its particular focus on the timeline for the transition to a carbon-neutral economy and how unambitious near-term goals threaten fundamental freedoms in the remaining transition-period. In the face of an unavoidable transition and of a limited budget of remaining CO2 emissions, freedom has an important intertemporal dimension. The Court acknowledges this dimension by embedding in the constitutional analysis of today’s measures the potential need for more severe future interventions and by imposing a procedural requirement on the legislature to allocate the remaining available emissions over time with sufficient foresight. This is a particularly compelling approach to protecting constitutional values without interfering too much in the political process. 

Climate change, on the one hand, calls for constitutional protection and an active role for constitutional courts. Due to its long time horizon, it is a problem that the political process tends to underestimate and address too late. The political­ system with its rather short legislative periods is institutionally geared toward short-term ­success; markets are considered dynamically inefficient in the face of current externalities that create increasing consequences over time; human perception systematically underestimates long-term ­risks compared to short-term benefits; and future generations do not have a voice in the political process. The German Constitution (GG) addresses the issue in its Art. 20a, calling on the state to protect the natural foundations of life ‘also in its responsibility for future generations’. The KSG ruling of the Federal Constitutional Court highlights the need for a transition to a carbon-neutral economy before the internationally agreed and legislatively adopted temperature limits are exceeded.

On the other hand, climate change is an inherently global problem and it is by no means clear that national constitutional law can really provide an answer. The challenge is no less than to transform the tragedy of the commons into a drama with a happy ending. Given Germany’s share of only about 2% of global CO2 emissions, the country can only make a small (direct) contribution. Also, its fair share of the remaining global CO2 emissions’ budget derived from the temperature targets depends on complicated questions of ‘global equity’. In light of these complexities, is there any standard to be found in constitutional law? The Court recognizes that national contributions to global CO2 reduction depend on political value judgements. At the same time, the Court convincingly derives from Art. 20a GG the state’s obligation to participate in international efforts, including their implementation, and not to compromise these endeavours. The existing international system of voluntary commitments under the Paris Agreement is based on trust and, ultimately, on a broad agreement on the respective national contributions. Complying with one’s own commitments preserves international trust. In evaluating national contributions, the Court resorts to the model of the German Advisory Council on the Environment which has calculated the remaining national CO2 emission budgets on the basis of a global per capita distribution and following the findings and scientific standards of the Intergovernmental Panel on Climate Change. This approach reflects a middle ground in the international discussion and corresponds with the ‘common but differentiated responsibility’ which is enshrined in Art. 3 No 1 UN Framework Convention on Climate Change 1992 and Art. 2 (2) Paris Agreement 2015. However, due to scientific uncertainties and political influence on the national budget, the model is explicitly not taken as a strict numerical threshold.

Achieving climate neutrality before critical temperature limits are exceeded and participating in the development of effective international solutions are key obligations under Article 20a GG. The critical temperature limits and the national share of the global CO2 residual budget derive from the interplay of general constitutional requirements, scientific evidence, and legal determinations already adopted under international and national law. This approach ensures that constitutional demands remain sensitive to scientific progress, developments in international law and political value judgments. Because of the uncertainties of scientific models and forecasts the Court ultimately finds no violation of substantive constitutional requirements under Art. 20a GG: The KSG embraces the temperature limits of the Paris Agreement as well as a commitment to the long-term goal of greenhouse gas neutrality by 2050 from the UN Climate Summit in 2019. It also includes a commitment to gradually reduce emissions by 55% (compared to the 1990 levels) in 2030 and, subsequently, in accordance with regulations to be adopted by the Federal Government. This reduction path was considered to still be within the legislative margin of discretion in view of the uncertainties—although the Court does characterise it as hesitant.

Before the KSG judgment, the discussion on constitutional aspects of climate change had focused not on Art. 20a GG but on the constitutional duties to protect the fundamental values of life, health and property. While the Court examines this aspect in detail at the beginning of the decision it finds it ultimately inconclusive not only because of scientific uncertainties but above all because climate adaptation measures can also be taken in the future to provide sufficient protection. Hence, the constitutional duties to protect are pertinent but are not (yet) violated by the KSG regime.

Even though the Court finds no violation of substantive requirements, the KSG was held partially unconstitutional because it does not adequately address the time-dimension of the path to greenhouse gas neutrality.

The crucial point is that—in view of the limited CO2 budget and the factual and normative necessity to achieve carbon-neutrality—a higher level of earlier budget consumption inevitably leads to more severe future restrictions with far-reaching effects on constitutional civil liberties in subsequent periods. Therefore, it is necessary to also take the time dimension into account when evaluating present measures. The Court captures the connection between today’s budget consumption and future restrictions in the notion of an ‘advance effect equivalent to an impairment’ of fundamental rights in the future (‘eingriffsgleiche Vorwirkung’). The constitutional task vested in the legislator is to accomplish an ‘intertemporal preservation of freedom’ (‘intertemporale Freiheitssicherung’). In the context of the proportionality test, the Court finds that the KSG entails a danger of unreasonable impairments of future fundamental rights. The danger of failing to meet the constitutional demands of an ‘intertemporal preservation of freedom’ triggers procedural requirements. The legislator is obliged to plan a predictable CO2 reduction path and thus to ensure a transparent and predictable route to carbon-neutrality. Importantly, the content of the plan remains a matter of political discretion and value judgment. This approach reflects the magnitude of the upcoming transformation and rightly calls for an active role of the state in setting the long-term framework for much-needed innovations. 

The KSG decision is historical because it translates the crucial time dimension of climate protection into constitutional requirements that, on the one hand, force legislators to extend their time horizon and chart a path to greenhouse gas neutrality, while, on the other hand, respecting the political nature of the many compromises that must be made along the way.


Martin Eifert holds the Chair of Public Law at the Faculty of Law, Humboldt-Universitaet zu Berlin.

This post is part of the series ‘Business Law and the Transition to a Net Zero Carbon Economy’. This series consists mainly of posts summarizing papers presented and presentations made at the 5th Annual Oxford Business Law Blog conference on ‘Business Law and the Transition to a Net Zero Carbon Economy’ which took place online on 25 to 27 May 2021. The recordings are available here. This post is forthcoming in Andreas Engert, Luca Enriques, Georg Ringe, Umakanth Varottil and Thom Wetzer (eds), Business Law and the Transition to a Net Zero Carbon Economy (CH Beck - Hart Publishing 2021) (forthcoming).