Tex. Ins. Code § 102.151

Any person or entity involved in the issuance of a qualified charitable gift annuity shall have immunity from suit, including both a defense to liability and the right not to bear the cost, burden, and risk of discovery and trial, as to any claim brought by or on behalf of the donor or the donor's heirs or distributees alleging that the issuance of a charitable gift annuity constitutes engaging in the business of insurance in this state. An interlocutory appeal may be taken if a court denies or otherwise fails to grant a motion for summary judgment that is based on an assertion of the immunity provided in this section.