Texas Government Code - GOV'T § 437.002. Commander-in-Chief

(a) The governor is the commander-in-chief of the Texas military forces, except any portion of those forces in the service of the United States.  The governor has full control and authority over all matters relating to the Texas military forces, including organization, equipment, and discipline.

(b) If the governor is unable to perform the duties of commander-in-chief, the adjutant general shall command the Texas military forces, unless the state constitution or other state law requires the lieutenant governor or the president of the senate to perform the duties of governor.