Under the terms of the Concordat between the Holy See and Spain, Catholic RE teachers must obtain a declaration of suitability prior to their appointment by the competent administrative authority. The bishop's authority to revoke any such statement, and the State's jurisdictional prerogative in overseeing such decisions, are matters of some dispute in Spanish courts. The Constitutional Court has found that the fundamental rights of applicants are not diminished by the fact that they are acting as religion teachers. In certain cases, however, the Court has highlighted that the right to transmit its beliefs through teaching is a key element of collective religious freedom that should prevail. The European Court of Human Rights (ECtHR) in cases "Fernandez Martinez v. Spain" (2014) and "Travaš v. Croacia" (2016) found that, by signing the employment contract, the applicants knowingly and voluntarily accepted a 'heightened duty' of loyalty towards the Church, limiting the scope of their fundamental rights. Following the judgements of the ECtHR, this paper shows how the Spanish system has dealt with collective religious freedom and employees' rights, providing a theoretical analysis of the legal grounds for the courts' judgements.