Tex. Election Code § 42.007: COMBINING INCORPORATED AND UNINCORPORATED TERRITORY.

A commissioners court may not establish a county election precinct containing territory inside a city with a population of 10,000 or more and unincorporated territory outside that city unless the commissioners court determines that either of the two areas:

(1) cannot constitute a separate election precinct of suitable size or shape that contains the permissible number of voters; or

(2) cannot be combined with other territory on the same side of the city boundary to form an election precinct of a suitable size or shape that contains the permissible number of voters without causing another election precinct to fail to meet those requirements.

Acts 1985, 69th Leg., ch. 211, Sec. 1, eff. Jan. 1, 1986.