Police officers have to be polite. They are required by law
However, penalties for rudeness are not envisaged. Help and protect – and politely too. This is how the work of the Czech police should ideally look like if the Ministry of the Interior’s vision were to be fulfilled. The motto “to help and protect” can be seen on the doors of police cars for now, but the new police law directly mandates the aforementioned courtesy. The new law establishes courtesy as a basic duty of a police officer.
Source : https://zpravy.aktualne.cz/policiste-musi-byt-zdvorili-narizuje-jim-to-zakon/