International criminal law recognizes certain defences, excuses and justifications that may be raised against a charge of genocide. These include mistake of fact, duress and necessity and self-defence. The defences are codified in detailed provisions of the Rome Statute but they are also derived from case law. The Rome Statute declares that an order to commit genocide is ’manifestly unlawful’ and therefore unavaible to an accused person. A defence of ’official capacity’ is explicitly excluded by article IV of the Convention whereby offenders must be punished ’whether they are constitutionally responsible rulers, public officials or private individuals’.