Giving people a great deal of freedom over how they live their lives, in and of itself, lends much scope for the egoistically inclined to act upon their instincts and to seek advantage at the expense of others. One way in which they might do this is by using the findings of behavioural science in order to manipulate others in an exchange relationship. In such circumstances, harms – or negative externalities – will be imposed upon the manipulated. I argue in this chapter that where people or organisations use the behavioural influences to further their aims, or indeed where the behavioural influences cause others to forgo what could be easily won benefits, there exists an intellectual justification for behavioural-informed regulation – or, in other words, for budge interventions. In this chapter, I further discuss some of the relevant trade-offs that must be considered when deciding whether or not to regulate, and outline the parameters of the budge framework with a few illustrative examples.