Tex. Natural Resources Code § 111.084

The operation of gathering systems for crude petroleum by pipeline or by truck in connection with the purchase or purchase and sale of crude petroleum is a business in the mode of the conduct of which the public is interested, and as such is subject to regulation by law. Therefore, it is provided that the business of purchasing or of purchasing and selling crude petroleum by the use of a gathering system for crude petroleum, whether by pipeline or by truck, shall not be conducted unless the person operating the gathering system being used in this manner in connection with this business is a common purchaser under this law and subject to the jurisdiction conferred on the commission over common purchasers.