Tex. Civil Practice and Remedies Code § 21.021: APPLICATION.

This subchapter applies to a county that:

(1) is part of two or more judicial districts, that has two or more district courts with regular terms, and that is part of a district in which a county borders on the international boundary of the United States and the Republic of Mexico;

(2) borders on the international boundary of the United States and the Republic of Mexico and that is in a judicial district composed of four counties;

(3) borders on the international boundary of the United States and the Republic of Mexico and that has three or more district courts or judicial districts wholly within the county; or

(4) borders on the Gulf of Mexico and that has four or more district courts or judicial districts of which two or more courts or districts are wholly within the county.

Acts 1985, 69th Leg., ch. 959, Sec. 1, eff. Sept. 1, 1985.