The framework and decisions in the League of Nations on 24 June 1921 on territorial autonomy, linguistic guarantees, demilitarisation and neutralisation were incorporated among others into an agreement between Finland and Sweden. The Council unanimously approved the terms of the agreement and annexed it to its decision on June 27th 1921. Under this agreement and decision, the League of Nations also had a role in monitoring the guarantees.
The most important international documents on Åland, including the Council’s discussion and decision of 27/6/1921, are available in various languages on the website of the Åland Cultural Foundation: https://kulturstiftelsen.ax/internationella-avtal/.