holder of the certificate and that he is in a position to exploit the variety in a serious and effective manner. A compulsory license may only be non-exclusive. It shall be granted under specific conditions, particularly as to its duration, its scope and the amount of the royalties thereunder. Such conditions may be modified by a decision of the competent court, at the request of the holder of the certificate or of the licensee. Article 23 Any transfer of the rights under a compulsory license shall be subject, on pain of nullity, to authorization from the competent court. Article 24 If the holder of a compulsory license does not comply with the conditions on which the license was granted, the holder of the certificate and, where appropriate, the other licensees may request the competent court to withdraw that license. Article 25 A variety essential to human or animal life or which involves public health may be exploited ex officio by any person who can give the necessary technical and professional guarantees. Ex officio exploitation shall be decided by an administrative order. Article 26 As from the day of publication of the administrative act which decides the ex officio exploitation of a plant variety certificate, any person who has the necessary technical and professional qualifications may request the grant of a license known as an “ex officio license.” Such license may only be non-exclusive. It shall be applied for and granted subject to the conditions laid down by regulation. An ex officio license shall be granted under specific conditions, particularly as to its duration and its scope. The royalties under an ex officio license shall be agreed by the parties or, failing agreement between them, their amount shall be laid down by the competent court. An ex officio license shall take effect as of the date of notification to the parties of the act granting the license. Article 27