Master Nationality Rule

The examples and perspective in this article deal primarily with the United Kingdom and do not represent a worldwide view of the subject. You may improve this article, discuss the issue on the talk page, or create a new article, as appropriate. (July 2021) (Learn how and when to remove this message)

The Master Nationality Rule is a consequence of Article 4 of the Convention on Certain Questions Relating to the Conflict of Nationality Laws of 1930, a treaty ratified by twenty-three parties.^[1] This provides that "a State may not afford diplomatic protection to one of its nationals against a state whose nationality such person also possesses".^[2]

In terms of practical effect, it means that when a multiple citizen is in the country of one of their nationalities, that country has the right to treat that person as if they were solely a citizen or national of that country. This includes the right to impose military service obligations or require an exit permit to leave.^[3]

Professor Eileen Denza states that the rule is a codification of a "classic rule" and, as of 2018, remains "modern state practice" internationally. The International Law Commission's 2006 draft Articles on Diplomatic Protection generally reaffirmed the rule.^[4]