Excessive reliance on CDR could breach legal guardrails and jeopardise net zero, warn Oxford law experts

A new interdisciplinary study led by University of Oxford researchers examines the international legal framework governing states’ reliance on carbon dioxide removal (CDR) in meeting climate targets – and identifies a series of legal ‘guardrails’ designed to ensure that such reliance does not undermine efforts to limit global warming.  

With temperatures reaching record levels across the world, the paper argues that while CDR will be an essential component of global climate action, heavy dependence on future removals carries significant risks if used as a substitute for ambitious shorter-term emissions cuts. Carbon dioxide removal means taking CO₂ out of the air and storing it (for example, by planting trees) so it no longer contributes to global warming. 

The authors analyse how the harm prevention principle and the standard of due diligence that attaches to it, clarified by the International Court of Justice in its 2025 Advisory Opinion on Climate Change, applies to states’ mitigation strategies. They find that this stringent, objective legal standard requires states not only to pursue deep and rapid greenhouse gas reductions but also to take a precautionary approach to the uncertainty associated with large-scale CDR deployment. Applying this due diligence standard, they conclude, will constrain states’ ability to rely on strategies that risk substantial overshoot of the Paris Agreement’s 1.5°C temperature goal – an overshoot that states are obliged to minimise in magnitude and duration. 

Study author Professor Lavanya Rajamani, of Oxford’s Faculty of Law, says: “In an uncertain world, some states are gambling on the future deployment of CDR techniques to meet their climate targets in place of more ambitious near-term mitigation measures. This approach risks overshooting the Paris temperature goal and causing serious, pervasive and irreversible climate harms. Our findings emphasise that near-term emissions reductions and feasible CDR strategies are not only ethical imperatives – they are legal requirements.” 

Co-author Dr Rupert Stuart-Smith, of the Oxford Sustainable Law Programme and the University’s Smith School of Enterprise and the Environment, adds: “States increasingly plan to meet their climate targets through large-scale removals, yet many of these plans rest on unclear assumptions and technologies that may not materialise. Legal guardrails are essential to avoid passing climate risks on to future generations and to ensure that CDR does not substitute for the emissions reductions urgently needed now.” 

Emerging from the legal framework are both substantive and procedural guardrails. Substantively, states must prioritise emissions reductions over removals, ensure that any CDR strategy is technically and socially feasible, minimise adverse impacts, and avoiding overreliance on removals carried out abroad (known as international credits). Procedurally, they must provide transparent information on projected emissions and removals, distinguish between different types of CDR, and disclose the assumptions underlying long-term mitigation strategies. 

The study’s findings demonstrate that international law already provides a clear framework for assessing states’ climate strategies, and that many existing plans fall short of these requirements. Aligning national mitigation efforts with this legal framework, say the authors, will demand a greater focus on near-term emissions cuts and increased transparency and realism in the use of CDR. 

The study, ‘Legal guardrails on states’ dependence on carbon dioxide removal to meet climate targets’, is published in the journal Climate Policy. The work is a collaboration between researchers from the University of Oxford, Imperial College London, the International Institute for Applied Systems Analysis in Austria, Humboldt University of Berlin, and the Potsdam Institute for Climate Impact Research.