A man who seduces a maiden who is not betrothed… (Exodus 22:15-16)
The courts are likewise required to judge the case of the seducer. The parameters provided by the Torah are specifically for an unbetrothed virgin. (Please remember that betrothal is more than what we call engagement; a betrothed woman would be considered married even though she has not yet moved in with her husband.) In this case, the seducer is required to marry the girl and provide her with the usual dowry. If the girl or her father objects to the union, the seducer must pay a fine of fifty silver shekels. (Why the father? Because the girl in this case is a minor. An adult woman would make her own choices and live with the consequences.)
While both the girl and her father have the right to refuse the marriage, the fine only goes to the father. If there is no father, the fine is forfeit. This is because the act was consensual. Granted, it didn’t have the father’s consent (which would be necessary to marry a minor), but the girl forfeited her claim to the fine by consenting to the act. (In the case of rape, the girl is entitled to the fine because it lacked her consent. See Talmud Kesubos 40a and Mitzvah #557.)
In addition to the standard fine of fifty silver shekels, the Talmud in Keubos (39a) clarifies that he also pays damages and for her embarrassment; these are variable amounts, based upon the individual circumstances of the case. Unlike the case of the rapist, the seducer may refuse the marriage and pay the fine.
This mitzvah applies to the ordained courts, since only they can impose fines under Torah law. It is discussed in the third and fourth chapters of the Talmudic tractate of Kesubos and is codified in the Shulchan Aruch in Even Ha’Ezer 177. The obligation to judge the case of a seducer is #220 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos.