It would be easy to assume that the European Patent Office (EPO) stands in the same relationship to the European Union as the USPTO does to the United States, but that’s actually wide of the mark. The EPO is a very strange beast indeed, as its Wikipedia entry makes clear:
The premises of the European Patent Office enjoy a form of extraterritoriality. In accordance with the Protocol on Privileges and Immunities, which forms an integral part of the European Patent Convention under Article 164(1) EPC, the premises of the European Patent Organisation, and therefore those of the European Patent Office, are inviolable. The authorities of the States in which the Organisation has its premises are not authorized to enter those premises, except with the consent of the President of the European Patent Office.