This paper addresses issues that arise from the recognition of private arbitrary power as a rule of law problem. It contrasts public with private arbitrary power, arguing that both ought to be a central preoccupation of any compelling conception of the rule of law. The paper explores the relationship between arbitrariness, freedom and consent in interactions involving private wrongs that fall short of being coercive (e.g. exploitation, harassment, manipulation). It makes the case for a pro-regulatory conception of the rule of law. That conception has been criticised as entailing intellectual sleight of hand, or as being ‘unnecessary’ where other values support the regulatory and welfare state. The paper illustrates by reference to the lack of regulation during the Covid-19 pandemic, and the latent state-scepticism in rule of law commentary during the pandemic, why both objections are misguided. Recognising the rule of law’s social dimension is a very ‘necessary’ turn in public law.