The Mosque–Cathedral of Córdoba was originally built by the Visigoths as the Basilica of Saint Vincent of Lérins. When the Muslims conquered Spain in 711 the Basilica was divided into Muslim and Christian halves: the arrangement that lasted until 784, when the Christian half was purchased by the Emir ‘Abd al-Rahman I, who demolished the entire structure and build the Grand Mosque of Córdoba on the site. When Córdoba returned to Christian rule in 1236 the building was converted into a church and a nave was added in the 16th century. Since the early 2000s Spanish Muslims have lobbied unsuccessfully to be allowed to pray in the cathedral.
In 2006 the Diocese of Córdoba paid €30 to register ownership of the mosque-cathedral. However, Córdoba City Council’s Secretary General, Valeriano Lavela Pérez, has written a report in which he rejects the claim and argues that the registration by the Diocese is of no legal effect: there is a summary here. Lavela says that the building does not belong to the Church nor to any other organisation or individual. He contends that the Church’s acquisition has no legal basis and cannot confer ownership, not only because the building has been a World Heritage Site since 1984 and therefore cannot be owned by anyone but because, in his view, the site’s true owners “are each and every citizen of the world from whatever epoch and regardless of people, nation, culture or race”. He notes that Article 132 of the Constitution and Article 6 of the Ley del Patrimonio de las Administraciones Públicas regard goods such as the Cordovan monument “inalienable”, “imprescriptible” and “outside the commerce of men” [al tiempo que lo sitúa fuera del comercio de los hombres].
His first contention seems extremely doubtful: I should be astonished if there were no legal owner of Durham Cathedral and Castle or of the individual properties in the City of Bath and the Old and New Towns of Edinburgh – all of which are on the current UNESCO list for the UK. His second is a matter of Spanish domestic legal principle on which I can have no worthwhile view. But the spat does have echoes of an earlier dispute between the Church and a commercial company, Sociedad Anónima del Ucieza, which had purchased a plot of land at Ribas de Campos that had once belonged to the former monastery of Santa Cruz de la Zarza and which included a church as an enclave.
In Sociedad Anónima del Ucieza v Spain  ECHR 1186 the Diocese of Valencia had registered the same church in the land register in its own name; and the company’s claim in the domestic courts to cancel the registration of the church and its annexes by the Diocese had been unsuccessful. The ECtHR concluded that the company had been a victim of the exercise of the right of registration granted by the Roman Catholic Church’s own canon law without any apparent justification and without the Diocese having mounted a challenge on the basis of its own asserted ownership rights when the property had been registered in 1979. Consequently, there had been a violation of A1P1 ECHR (peaceful enjoyment of property): we noted the case here.
I suspect that this is another such clash. I also suspect that this is only the beginning; and it will be interesting to see how the dispute develops.