Wyo. Stat. § 14-2-608: Challenge after expiration of period for rescission.

(a) After the period for rescission under W.S. 14-2-607 has expired, a signatory of an acknowledgment of paternity or denial of paternity may commence a proceeding to challenge the acknowledgment or denial only:

(i) On the basis of fraud, duress or material mistake of fact; and

(ii) Within two (2) years after the acknowledgment or denial is filed with the state office of vital records.

(b) A party challenging an acknowledgment of paternity or denial of paternity has the burden of proof.