The federal loyalty in Spain is an unwritten constitutional principle that binds the State and the Autonomous Communities in their intergovernmental relations, as well as in the exercise of their competencies. The jurisprudence of the Constitutional Court and the scholars acknowledge its implicit existence, linking it to other foundational principles of the territorial system such as solidarity, collaboration, and its specific manifestations (cooperation, coordination, and mutual aid). This paper examines the various manifestations of this principle in the Statutes of Autonomy, many of which have included references to loyalty since the reforms introduced at the beginning of this century. The aim of this study is to demonstrate whether these references have a legal value or, on the contrary, they remain merely symbolic