This article seeks to analyze the project for the international convention on the protection of minority rights, which was proposed by André Mandelstam at the Institut de Droit International (IDI) in 1928. In this project, the author used the concept of non-territorial autonomy borrowed from the works of the Austro-Marxists Otto Bauer and Karl Renner. A Russian international lawyer in emigration, André Mandelstam had initially been involved in the implementation of elements of non-territorial autonomy to protect the Christian population of the Ottoman empire. Mandelstam’s proposed convention assumed that personal autonomy, reduced to the protection of minorities from cultural and linguistic assimilation, would be a compromise between protecting minorities and preventing them from undermining the unity of the state. However, the demand for international protection of minorities was not accompanied by any enforcement mechanism. The project underwent serious revisions as it was discussed by a group of international lawyers. In its final version, the text retained only those of the original articles, which referred to individual human rights. Thus, Mandelstam’s attempt to make his convention acceptable for all participating states resulted in omission of the very concept of personal autonomy in the final version of the proposed document.