As far as the effects of Brexit on the cooperation in criminal law matters between France and the UK are concerned, police cooperation should be distinguished from judicial cooperation. The police cooperation in the cross-Channel border area is currently based on agreements concluded outside the EU legal framework. It should therefore be hardly affected by Brexit. Nevertheless, some of the provisions of these arrangements being inconsistent with EU legislation, Brexit may give rise to some reconsiderations. Furthermore, the efficiency of the post-Brexit cooperation between French and British police authorities will depend on the continued involvement of British forces in EU instruments and organs – except, perhaps, as regards counter-terrorism police cooperation which is mainly operated in ad hoc compounds and through ad hoc proceedings. As regards judicial cooperation in criminal matters, a hard Brexit will certainly lead to a resurgence of the difficulties encountered under the Council of Europe instruments’ cooperation regime. Therefore, both countries share an interest in trying to preserve the arrangements found through the Lisbon Protocol 36 settlement. © 2017, Springer Science+Business Media Dordrecht.