This paper considers the justifiability of criminalising anti-social behaviour through two-step prohibitions such as the Anti-Social Behaviour Order (ASBO). The UK government has recently proposed to abolish and replace the ASBO; however, the proposed new orders would retain many of its most controversial features. The paper begins by criticising the definition of anti-social behaviour employed in both the current legislation and the new proposals. This definition is objectionable because it makes criminalisation contingent upon the irrational judgements of (putative) victims, and (...) its often modest preventive benefits come at a high cost to citizens’ liberty and autonomy. The paper then goes on to propose a new definition of anti-social behaviour that would meet these objections: that is, as a course of conduct that causes others to experience serious and justifiable anxiety about the safety of their local community. Whilst this definition identifies a serious form of wrongdoing, its precise scope is inevitably uncertain. The paper thus concludes that we have good reason to use two-step prohibitions such as the ASBO to regulate such conduct, so as to enable the use of the criminal law against it whilst minimising possible concerns of legality arising from the proposed definition’s uncertain scope. (shrink)