新渡戶稻造
Finland, however, declined to cede the islands and instead offered the islanders an autonomous status. Nevertheless, the residents did not approve the offer, and in 1921 the dispute over the islands went before the newly formed League of Nations. The latter decided that Finland should retain sovereignty over the province, but that the Åland Islands should be made an autonomous territory. One of the important proponents of a diplomatic solution to the case was Nitobe Inazō, who was one of the Under-Secretaries General of the League and the director of the International Bureaux Section, in charge of the International Committee on Intellectual Cooperation. The Åland convention of 20 October 1921, signed by Sweden, Finland, Germany, the United Kingdom, France, Italy, Denmark, Poland, Estonia, and Latvia, was the first international agreement achieved by the League. Thus, Finland was obliged to ensure the residents of the Åland Islands the right to maintain the Swedish language, as well as their own culture and local traditions. The convention of 1921 established the neutral status of Åland by international treaty, prohibiting the placing of military installations or forces on the islands. Åland's Regional Assembly convened for its first plenary session in Mariehamn on June 9, 1922; today, the day is celebrated as Self-Government Day of Åland.