I think the relevant portions for this issue would be Article 45 and part of Article 42:
The rights conferred by the provisions of the present Section on the non-Moslem minorities of Turkey will be similarly conferred by Greece on the Moslem minority in her territory.
The Turkish Government undertakes to take, as regards non-Moslem minorities, in so far as concerns their family law or personal status, measures permitting the settlement of these questions in accordance with the customs of those minorities.
These measures will be elaborated by special Commissions composed of representatives of the Turkish Government and of representatives of each of the minorities concerned in equal number. In case of divergence, the Turkish Government and the Council of the League of Nations will appoint in agreement an umpire chosen from amongst European lawyers.