The Czech Personal Data Protection Office issued an opinion on the situation when persons must identify themselves when entering certain buildings (i.e. by showing their ID or providing other personal data). 

The Office declares that protection of property is an important right of every subject, and therefore, collecting a certain amount of personal information to protect the property and to subsequently identify the person entering the building is a legitimate measure. Such personal data shall only be collected in the scope necessary and should be kept for a reasonable time period only (no more than a few weeks). It is sufficient to require only the first and last name of the subject entering the building. It is unacceptable to make copies of personal ID cards without the explicit consent of the person. 

Collection of personal data in the scope described above does not have to be notified to the Office. The data processor is obliged to properly inform data subjects of the scope and reasons for their personal data processing.