Okla. Stat. tit. 43, § 10

If the judge or clerk of the district court before whom application for a marriage license is made shall be in doubt of the legal capacity of the parties for whose marriage a license is sought, to enter into the marriage relation, such judge or clerk shall require additional evidence to that contained in the application, and may swear and examine witnesses or require affidavits in proof of the legality of such marriage, and unless satisfied of the legality thereof, he shall not issue a license therefor.