Whether irregularity is contracted by marrying one who is not a virgin?

Objections

Objection 1 : It would seem that irregularity is not contracted by marrying one who is not a virgin. For a man's own defect is a greater impediment to him than the defect of another. But if the man himself who marries is not a virgin he does not become irregular. Therefore much less does he if his wife is not a virgin.
Objection 2 : Further, it may happen that a man marries a woman after corrupting her. Now, seemingly, such a man does not become irregular, since he has not divided his flesh among several, nor has his wife done so, and yet he marries a woman who is not a virgin. Therefore this kind of bigamy does not cause irregularity.
Objection 3 : Further, no man can become irregular except voluntarily. But sometimes a man marries involuntarily one who is not a virgin, for instance when he thinks her a virgin and afterwards, by knowing her carnally, finds that she is not. Therefore this kind does not always cause irregularity.
Objection 4 : Further, unlawful intercourse after marriage is more guilty than before marriage. Now if a wife, after the marriage has been consummated, has intercourse with another man, her husband does not become irregular, otherwise he would be punished for his wife's sin. Moreover, it might happen that, after knowing of this, he pays her the debt at her asking, before she is accused and convicted of adultery. Therefore it would seem that this kind of bigamy does not cause irregularity.