(a) An insurance company may invest in:
(1) a bond, evidence of indebtedness, or other obligation of the United States;
(2) a bond, evidence of indebtedness, or other obligation guaranteed as to principal and interest by the full faith and credit of the United States;
(3) a bond, evidence of indebtedness, or other obligation of an agency or instrumentality of the United States government; and
(4) subject to Subsections (b) and (c), a bond, evidence of indebtedness, or other obligation of a governmental unit in the United States, Canada, or any province or municipality of Canada, or of an instrumentality of one of those governmental units.
(b) An insurance company may not invest in a bond, evidence of indebtedness, or other obligation under Subsection (a)(4) if the governmental unit or instrumentality is in default in the payment of principal of or interest on any of the governmental unit's or instrumentality's obligations.
(c) An insurance company's investments in the obligations of a single governmental unit or instrumentality under Subsection (a)(4) may not exceed 20 percent of the company's capital and surplus.