Apparently, the Governor and people of Texas have forgotten that their readmission to the United States of America came with the conditions set forth in the Texas Re-Admission Act:
http://www.tsl.state.tx.us/ref/abouttx/secession/30march1870.html
Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That the said State of Texas is entitled to representation in the Congress of the United States: Provided, That before any member of the legislature of said State shall take or resume his seat, or any officer of said State shall enter upon the duties of his office he shall take and subscribe and file in the office of the secretary of State of Texas, for permanent preservation, an oath or affirmation in the form following: "I, ____ ____, do solemnly swear (or affirm) that I have never taken an oath as a member of Congress, or as an officer of the United States, or as a member of any State legislature, or as an executive or judicial officer of any State, to support the Constitution of the United States, and afterward engaged in insurrection or rebellion against the same, or given aid or comfort to the enemies thereof, so help me God"; or under the pains and penalties of perjury (as the case may be); or such person shall, in like manner, take, subscribe. and file the following oath or affirmation: "I, ____ ____, do solemnly swear (or affirm) that I have, by act of Congress of the United States, been relieved from the disabilities imposed upon me by the fourteenth amendment of the Constitution of the United States, so help me God"; or under the pains and penalties of perjury (as the case may be); which oaths or affirmations shall be taken before, and certified by, any officer lawfully authorized to administer oaths.
And any person who shall knowingly swear or affirm falsely in taking either of such oaths or affirmations, shall be deemed guilty of perjury, and shall be punished therefor by imprisonment not less than one year, and not more than ten years, and shall be fined not less than one thousand dollars, and not more than ten thousand dollars.
In a nutshell, the Texas Governor is specifically prohibited from supporting insurrection or rebellion against the United States of America, and he is in violation of his oath.