Abstract: We examine exceptional cases in which judges are called upon to pass judgment on the constitution itself. There are three groups of cases. First, in exceptional cases the validity of the constitution and the legal order is thrown into dispute. The court is asked to rule on the legitimacy of the constitution and, by derivation, on the standing of the court and the legal authority of the judge. Second, on some occasions the judge is asked to rule on the transition from one constitutional order to another. This can occur in the aftermath of a revolution, or when the state is acceding to a new constitutional order. Third, there are some cases in which the health of the constitutional order requires the judge to act not merely beyond the law, as it were, but actually contrary to the law. The judge must act contrary to the rules of the legal order, precisely in order to preserve the health of the legal order. We claim that "constitutional decisionism" is inevitable in all three groups of cases. Courts sometimes have no option but to take it upon themselves to rule upon, and indeed to participate in constituting, the validity of the very constitutional order that gives them their authority, in a kind of bootstrapping.