In this paper I explore the role of mutual recognition between Spanish autonomous regions. The case of Spain is interesting from a comparative standpoint because regions enjoy important competences in the field of market regulation, the implementation of which can create risks in terms of market integration. These were traditionally dealt with by means of a constitutional provision that prohibits regional measures that restrict the exercise of the freedoms of movement under a proportionality standard of review (Article 139 of the Constitution). In 2013 the Spanish Parliament decided to go beyond that and passed a law establishing a region-of-origin rule. This was subsequently declared unconstitutional by the Constitutional Court, by virtue of the principle of regional autonomy (Article 2 of the Constitution). This story might show the scope, limits and constitutional problems of mutual recognition in a multilevel administrative State.