Planetary constitutionalism: Can (German) constitutional law save the planet?

Abstract Constitutional and rights-based climate litigation has led to significant doctrinal developments in several jurisdictions over the last decade. These developments have drawn considerable attention to climate change and climate law, but they risk overshadowing other urgent planetary crises. Earth-system science indicates that humanity has already transgressed seven of the nine planetary boundaries, of which climate change is only one. In response to these insights, this article introduces the concept of planetary constitutionalism. Building on earlier notions of environmental constitutionalism while also moving beyond them, the article draws on de constitutione ferenda proposals in Switzerland and Germany to theorize how national constitutions could explicitly establish legal limits on the planetary footprint of their economies, including externalized environmental harm. Given the limited prospects for explicit constitutional reform, the article then examines the interpretive potential of constitutional rights and constitutional environmental provisions in Germany to establish planetary legal limits. Drawing on debates already unfolding in German scholarship, as well as arguments advanced in Germany’s first constitutional biodiversity case, the article analyzes whether legal doctrines developed in climate litigation—most notably the much-debated concept of intertemporal guarantees of freedom—can also be applied to the second core planetary boundary, biosphere integrity, and whether they can extend to the full planetary footprint of a state. The article reaches a nuanced conclusion, highlighting both the significant contributions and the substantial limitations of German constitutional doctrine in defining “fair” planetary legal limits and governing the extraterritorial planetary footprint, while emphasizing the need for further research on planetary constitutionalism in Germany and beyond.