Tex. Estates Code § 1106.006

(a) Letters of guardianship existing on September 1, 1993, that were issued to a nonresident guardian without the procedure or any part of the procedure provided in this chapter, or without a notice or citation required of a resident guardian, are validated as of the letters' dates, to the extent that the absence of the procedure, notice, or citation is concerned. An otherwise valid conveyance, mineral lease, or other act of a nonresident guardian qualified and acting in connection with the letters of guardianship and under supporting orders of a county or probate court of this state is validated.

(b) This section does not apply to letters of guardianship, a conveyance, a lease, or another act of a nonresident guardian under this section if the absence of the procedure, notice, or citation involving the letters, conveyance, lease, or other act of the nonresident guardian is an issue in a lawsuit pending in this state on September 1, 1993.