From "A History of Ireland and Her People" by Eleanor Hull, 1931
ARTICLES OF AGREEMENT FOR A TREATY BETWEEN GREAT BRITAIN AND IRELAND.
Article 11. Until the expiration of one month from the passing of the Act of Parliament for the ratification of this instrument, the powers of the Parliament and the Government of the Irish Free State shall not be exercisible as respects Northern Ireland and the provisions of the Government of Ireland Act, 1920, shall, so far as they relate to Northern Ireland, remain of full force and effect, and no election shall be held for the return of members to serve in the Parliament of the Irish Free State for constituencies in Northern Ireland, unless a resolution is passed by both Houses of the Parliament of Northern Ireland in favour of the holding of such elections before the end of the said month.
Article 12. If before the expiration of the said month, an address is presented to His Majesty by both Houses of the Parliament of Northern Ireland to that effect, the powers of the Parliament and Government of the Irish Free State shall no longer extend to Northern Ireland, and the provisions of the Government of Ireland Act, 1920 (including those relating to the Council of Ireland) shall so far as they relate to Northern Ireland, continue to be of full force and effect, and this instrument shall have effect subject to the necessary modifications.
Provided that if such an address is so presented a Commission consisting of three persons, one to be appointed by the Government of the Irish Free State, one to be appointed by the Government of Northern Ireland, and one who shall be Chairman to be appointed by the British Government shall determine in accordance with the wishes of the inhabitants, so far as may be compatible with economic and geographic conditions, the boundaries between Northern Ireland and the rest of Ireland, and for the purposes of the Government of Ireland Act, 1920, and of this instrument, the boundary of Northern Ireland shall be such as may be determined by such Commission.