Article 21 Precedence as between consular officers of a consular post The order of precedence as between the consular officers of a consular post and any change thereof shall be notified by the diplomatic mission of the sending State or, if that State has no such mission in the receiving State, by the head of the consular post, to the Ministry for Foreign Affairs of the receiving State or to the authority designated by that Ministry. Article 22 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among persons having the nationality of the receiving State except with the express consent of that State which may be withdrawn at any time. 3.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. Article 23 Persons declared “non grata” 1. The receiving State may at any time notify the sending State that a consular officer is persona non grata or that any other member of the consular staff is not acceptable. In that event, the sending State shall, as the case may be, either recall the person concerned or terminate his functions with the consular post. 2. If the sending State refuses or fails within a reasonable time to carry out its obligations under paragraph 1 of this article, the receiving State may, as the case may be, either withdraw the exequatur from the person concerned or cease to consider him as a member of the consular staff. 3. A person appointed as a member of a consular post may be declared unacceptable before arriving in the territory of the receiving State or, if already in the receiving State, before entering on his duties with the consular post. In any such case, the sending State shall withdraw his appointment. 4. In the cases mentioned in paragraphs 1 and 3 of this article, the receiving State is not obliged to give to the sending State reasons for its decision. Article 24 Notification to the receiving State of appointments, arrivals and departures 1. The Ministry for Foreign Affairs of the receiving State or the authority designated by that Ministry shall be notified of: 10