Tex. Natural Resources Code § 101.051

Subject to the approval specified in Section 101.052 of this code, the Commissioner of the General Land Office, on behalf of the State of Texas or of any fund belonging to the state, may execute contracts committing to the agreements declared lawful by the provisions of this chapter (1) the royalty interests in oil or gas or both reserved to the state, or any fund of the state, by law, in any patent, in any contract of sale, or under the terms of any oil and gas lease lawfully issued by an official, board, agent, agency, or authority of the state or (2) the free royalty interests, whether leased or unleased, reserved to the state pursuant to Section 51.201 or 51.054 of this code.