Tex. Bus. Orgs. Code § 21.208

Subject to the certificate of formation, a shareholder of a corporation incorporated before September 1, 2003, has a preemptive right to acquire unissued or treasury shares of the corporation to the extent provided by Sections 21.204, 21.206, and 21.207. After September 1, 2003, a corporation may limit or deny the preemptive right of the shareholders of the corporation by amending the corporation's certificate of formation.