Not that I wish it for myself, but polygamy should be legal. Anything else is religious descrimination. The one man/one wife rule came from some creeds of some religions; other creeds and other religions permit polygamy (although most of those do not permit polyandry).
It is not the business of government to decree how many spouses one may have unless they can come up with a reason that is not founded in judaeo-christian scriptures. The government can, and should:
- Come up with a rule saying that all marriage partners must consent to the addition of a new marital partner. A person who is married and marries another without the consent of the other marital partner is guilty of bigamy.
- Come up with laws regarding the division of assets in the case of divorce.
- Figure out what to do if one partner wants to divorce another partner but other partners do not (could get very messy).
Individial religions can recognize multiple marriages or not as their creeds dictate and impose religious sanctions on those of their congregation who disobey, much like Catholics who divorce get sanctioned.
That said, the mainstream(ish) religions and creeds I know of that permit polygamy seem even more deluded and wacky than the ones that don't. But if the first amendment means anything at all, Morons and Muslims should be permitted multiple wives.