Montesquieu
 

XXVI.10 In which case one must follow the civil law which permits, and not the religious law which forbids

When a reli­gion that for­bids poly­gamy is intro­du­ced into a coun­try where it is per­mit­ted, we do not believe, spea­king only poli­ti­cally, that the coun­try’s law should allow a man who has seve­ral wives to embrace that reli­gion, unless the magis­trate or the hus­band com­pen­sa­tes them by in some way res­to­ring their civil sta­tus to them. Otherwise their situa­tion would be deplo­ra­ble ; they would only have obeyed the laws, and would find them­sel­ves depri­ved of society’s grea­test advan­ta­ges.