Persona non grata is a Latin phrase which literally means “an unwelcome person.” It is a phrase which is used both in legal and non-legal settings.
In the legal sense, the phrase has a specific meaning in the context of diplomacy. Pursuant to the Vienna Convention on Diplomatic Relations, a State may at any time and without explanation declare any member of a diplomatic staff persona non grata. A person so declared is no longer welcome in that country and is usually forced to return to his or her native country. If not recalled, the receiving State “may refuse to recognize the person concerned as a member of the mission.
In the non-legal sense, the phrase is commonly used to refer to people who are generally unwelcome, i.e. an uninvited dinner guest, and also those who are no longer welcome in a group due to their actions, i.e. a police officer who snitches on his colleagues.
“The Russian Foreign Ministry has declared a Finnish diplomat persona non grata for helping a Finnish citizen illegally take his child out of Russia.”