It is not against the law to have employees be identified by nationality so long as they are harassed  or discriminated against on that basis, and there is some reasonable reason for displaying nationalities. Many hospitalities companies (amusement parks; hotels) and day/sleepaway camps do this, to make guests from other countries/cultures more comfortable and given them someone from their own culture they can connect to if they want). The important point is, it's only harassment or discrimination, not identification of national origin, that is illegal.