Tex. Code Crim. Proc. art. 42.17

When a treaty is in effect between the United States and a foreign country providing for the transfer of convicted offenders who are citizens or nationals of foreign countries to the foreign countries of which they are citizens or nationals, the governor is authorized, subject to the terms of such treaty, to act on behalf of the State of Texas and to consent to the transfer of such convicted offenders under the provisions of Article IV, Section 11 of the Constitution of the State of Texas.