This paper investigates how rule violations that contributed to the Chernobyl nuclear disaster were able to happen. Bringing to the surface what is implicit in historical documents, we argue that six excuses can be identified that could have allowed the operators to rationalise their rule violations. These excuses could have affected how the operators interpreted the applicability of the rules to the situation(s) they were involved in, leading them to ultimately violate the operational rules. As a theoretical consequence, rule-following as (com)pliance or obedience is to be taken as a necessary but insufficient condition of rule-following. As a practical consequence, the concept of 'excuses' can also help to anticipate as well as prevent rule-breaking behaviour in similar future cases.
