Perhaps they are thinking about this OT policy: Remember Israelite men could divorce their wives for reasons other than adultery (which was punishable by a death sentence unless you are the king and his paramour)
Remarriage of Divorced Mates. Deuteronomy 24:1-4 also stipulated that the divorced woman “must go out of his house and go and become another man’s,” meaning that she was eligible for remarriage. It was also stated: “If the latter man has come to hate her and has written out a certificate of divorce for her and put it in her hand and dismissed her from his house, or in case the latter man who took her as his wife should die, the first owner of her who dismissed her will not be allowed to take her back again to become his wife after she has been defiled; for that is something detestable before Jehovah, and you must not lead the land that Jehovah your God is giving you as an inheritance into sin.” The former husband was barred from taking the divorced wife back, perhaps in order to prevent the possibility of any scheming between him and this remarried wife to force her divorce from her second husband or to cause his death, thereby allowing for remarriage with her previous husband. If her former marriage mate took her back, it would be an unclean thing in God’s eyes; the first husband would make himself look foolish because he had dismissed her as a woman in whom he had found “something indecent” and then, after she had been lawfully joined to another man and used as his wife, he took her back once again.
Doubtless the very fact that the original husband could not remarry his divorced wife after she became another man’s, even if that man divorced her or died, made the husband contemplating divorce action think seriously before acting to end the marriage. (Jer 3:1) However, nothing was said that would prohibit him from remarrying his divorced wife if she had not remarried after the legal severance of their marriage tie.