Whether it is lawful for a bigamist to receive a dispensation?

Objections

Objection 1 : It would seem unlawful for a bigamist to be granted a dispensation. For it is said (Extra, De bigamis, cap. Nuper): "It is not lawful to grant a dispensation to clerics who, as far as they could do so, have taken to themselves a second wife."
Objection 2 : Further, it is not lawful to grant a dispensation from the Divine law. Now whatever is in the canonical writings belongs to the Divine law. Since then in canonical Scripture the Apostle says (1 Tim. 3:2): "It behooveth . . . a bishop to be . . . the husband of one wife," it would seem that a dispensation cannot be granted in this matter.
Objection 3 : Further, no one can receive a dispensation in what is essential to a sacrament. But it is essential to the sacrament of order that the recipient be not irregular, since the signification which is essential to a sacrament is lacking in one who is irregular. Therefore he cannot be granted a dispensation in this.
Objection 4 : Further, what is reasonably done cannot be reasonably undone. If, therefore, a bigamist can lawfully receive a dispensation, it was unreasonable that he should be irregular: which is inadmissible.