Yea it is,though:
Sec. 7. COMMANDER-IN-CHIEF OF MILITARY FORCES; CALLING FORTH MILITIA. He shall be Commander-in-Chief of the military forces of the State, except when they are called into actual service of the United States. He shall have power to call forth the militia to execute the laws of the State, to suppress insurrections, and to repel invasions.
Constitution of the State of Texas (1876)
What about the Texas State Guard?