Texas constitution
Article 5: judicial department
Section 7(a)

(i) The legislature, the Judicial Districts Board, or the Legislative Redistricting Board may not redistrict the judicial districts to provide for any judicial district smaller in size than an entire county except as provided by this section. Judicial districts smaller in size than the entire county may be created subsequent to a general election where a majority of the persons voting on the proposition adopt the proposition "to allow the division of ___________ County into judicial districts composed of parts of ___________ County." No redistricting plan may be proposed or adopted by the legislature, the Judicial Districts Board, or the Legislative Redistricting Board in anticipation of a future action by the voters of any county.