Article 90 Chicago Convention

Adoption and amendment of Annexes

(a) The adoption by the Council of the Annexes described in Article 54, subparagraph (1), shall require the vote of two-thirds of the Council at a meeting called for that purpose and shall then be submitted by the Council to each contracting State. Any such Annex or any amendment of an Annex shall become effective within three months after its submission to the contracting States or
at the end of such longer period of time as the Council may prescribe, unless in the meantime a majority of the contracting States register their disapproval with the Council.

(b) The Council shall immediately notify all contracting States of the coming into force of any Annex or amendment thereto.

See also: Article 89 Chicago Convention