The coexistence of several layers of fundamental rights with different goals, plus procedures for protecting fundamental rights in the courts that differ in scope, makes for a particularly complex situation. That situation is even more complicated in the Area of Freedom, Security and Justice, since it raises particularly sensitive issues for fundamental rights. Furthermore, the mutual recognition principle implies that decisions taken in one Member State are recognised and executed in any other Member State based on the presumption that all Members States have a sufficient level of fundamental rights protection. Hence, it is of paramount importance to ascertain whether sufficient protection of fundamental rights is guaranteed in the AFSJ, what are its core elements and what are the problems related to its operation in practice. Within that framework, this chapter discusses whether the CJEU is building a European standard of fundamental rights in the AFSJ. To that end, it examines, first, how the CJEU is relying on general principles and secondary law to strengthen the standard of fundamental rights, and second, how that standard is adapted to horizontal cooperation in a scenario of mutual trust.