The carbon budget compatible with the Paris Agreement temperature target is rapidly depleting. Sufficient net CO₂ removal can rein in excess temperature increase. Where legislators opt for economic instruments to enable net CO₂ removal, which assumptions about decision-making behaviour should they apply? Though traditional law and economics suggests that subjects of the law are typically rational maximisers, puzzling evidence from emissions trading systems suggest that we may have to consider alternative assumptions such as those offered by behavioural law and economics. Based on the idea that loss aversion may have affected firms subject to emissions trading, this article explores what the existence of loss averse preferences could mean for the efficacy of offering either charges or subsidies to incentivise CO₂ removal. It argues that where decision makers exhibit loss averse rather than rational maximising preferences, charges may present more effective incentive than certain subsidies. This finding is of particular relevance for facilitating net negative emissions because legislators are currently opting for subsidies to incentivise CO₂ removal. Predicting decision-making behaviour is, however, fraught with uncertainty, implying a risk for the environmental effectiveness of relying on pure economic instruments. Legislators should account for that behavioural uncertainty when choosing the proper legislative tool to enable net CO₂ removal.