Article 22 Vienna Convention on Consular Relations
Nationality of consular officers
1.Consular officers should, in principle, have the nationality of the sending State.
2.Consular officers may not be appointed from among persons having the nationality of the receiving State except with the express consent of that State which may be withdrawn at any time.
3.The receiving State may reserve the same right with regard to nationals of a third State who are not also nationals of the sending State.
See also: Article 21 Vienna Convention on Consular Relations