NYSentencing

§ 255.20   Unlawfully  procuring  a marriage license, bigamy, adultery:
               defense.
  In  any  prosecution  for  unlawfully  procuring  a  marriage license,
bigamy, or adultery, it is an affirmative  defense  that  the  defendant
acted under a reasonable belief that both he and the other person to the
marriage or prospective marriage or to the sexual  intercourse,  as  the
case may be, were unmarried.