(a) An insurance carrier’s notice of refusal to pay benefits under § 409.021 must specify the grounds for the refusal.
(b) The grounds for the refusal specified in the notice constitute the only basis for the insurance carrier’s defense on the issue of compensability in a subsequent proceeding, unless the defense is based on newly discovered evidence that could not reasonably have been discovered at an earlier date.

(c) An insurance carrier commits an administrative violation if the insurance carrier does not have reasonable grounds for a refusal to pay benefits, as determined by the commissioner.
(d) In this subsection, the terms “custodial officer,” “detention officer,” “emergency medical technician,” “firefighter,” and “peace officer” have the meanings assigned by § 607.051, Government Code. In addition to the other requirements of this section, if an insurance carrier’s notice of refusal to pay benefits under § 409.021 is sent in response to a claim for compensation resulting from a custodial officer’s, a detention officer’s, an emergency medical technician’s, a firefighter’s, or a peace officer’s disability or death for which a presumption is claimed to be applicable under Subchapter B, Chapter 607, Government Code, the notice must include a statement by the carrier that:
(1) explains why the carrier determined a presumption under that subchapter does not apply to the claim for compensation; and
(2) describes the evidence that the carrier reviewed in making the determination described by Subdivision (1).
(d-1) An insurance carrier has not committed an administrative violation under § 409.021 if the carrier has sent notice to the employee as required by Subsection (d) of this section or § 409.021(a-3).