Tex. Educ. Code § 51.242

No person may refuse or fail to leave a building under the control and management of a public agency, including a state-supported institution of higher education, during those hours of the day or night when the building is regularly closed to the public, upon being requested to do so by a guard, watchman, or other employee of a public agency, including a state-supported institution of higher education, controlling and managing the building or property, if the surrounding circumstances are such as to indicate to a reasonable person that the individual or individuals have no apparent lawful business to pursue.