(a) This section applies only to a state agency in the executive branch of state government that is required to participate in the comptroller's contracts for travel services.
(b) Except as provided by comptroller rule, a state agency may not:
(1) purchase commercial airline or rental car transportation if the amount of the purchase exceeds the amount of the central travel office's contracted fares or rates; or
(2) reimburse a person for the purchase of commercial airline or rental car transportation for the amount that exceeds the amount of the central travel office's contracted fares or rates.
(c) The comptroller shall educate state agencies about this section.
(d) The comptroller shall audit travel vouchers under Chapter 403 for compliance with this section.
(e) The comptroller shall adopt rules related to exemptions from the prohibition prescribed by Subsection (b).