Politics in France during the last years of Louis XV's reign was dominated by the Brittany affair, one of the most curious and ultimately destructive of the disputes involving the king and his parlements. The affair was triggered by the need to register the financial declaration of 21 November 1763, which provoked a serious clash with the Parlement of Rennes, leading to the resignation of that court in May 1765. In this charged atmosphere, six Breton magistrates were arrested and accused of conspiring against the crown. At the centre of the affair was the procureur général of the Parlement, Louis Rene Caradeuc de La Chalotais, who was also accused of sending threatening letters to the king. Throughout 1766, the government employed a whole series of methods, some of dubious legality, in order to try the six judges, but its efforts were in vain. Failure exposed the men responsible for implementing this policy – headed by the commandant of the province, the duc d'Aiguillon – to the revenge of the magistrates, culminating in the trial of the duc himself before the Parlement of Paris in 1770.

At the end of the nineteenth century, the Brittany affair stimulated a lively historiographical debate, serving as something of a test case for wider arguments about the reforming monarchy and parlementaire opposition. Great emphasis was placed upon the personalities of the two principal protagonists, and the crisis was viewed, in part, as an extension of a private quarrel.