Legal status of polygamy in the US - justification on other than moral grounds?

Polyandry exists, but is very rare; mostly found in the Himalaya, apparently.

That’s fascinating, and quite disturbing at the same time! I couldn’t imagine being married to the same woman as my brother! Makes more sense I guess for the women to have multiple husbands rather than the other way around though

A guess: brain drain of educated men (women) who can’t find wives (husbands) if polygyny (polyandry) becomes widespread?

If they’re educated, they’re more likely to be in the plus-spouse group than the minus-spouse group.

There’s now nothing to stop a bunch of like-minded people from entering into a “conjugal partnership”; business partnerships didn’t need special legislation to make them happen; the mechanisms for adding and substracting partners are set out not in legislation but in the partnership agreement, and I don’t see why a conjugal partnership couldn’t work the same way now.

The point of marriage law is not so much that it regulates relationships between the two spouses but that it regulates relationships between the spouses together and wider society. Existing partnership law has nothing to say about paternity, about inheritance, about next of kin rights, all areas that marriage law has a great deal to say about. I’m not saying that there is nothing in partnership law that couldn’t usefully be adapted to a polygamy law, but I suspect a fully-worked-out polygamy code would look a lot more like a family code with borrowings from partnership law than the other way around.

This true only to the extent that we still assume that women have aneed to be supported by men. I am aware of 3 different multimarriages, in reality only, not legally, where the group is together for the purpose of pooling their social security checks to live above the poverty line.

. . . and, depending on the local law and the particular circumstances, such a group might not want to be married, legally speaking, since if they were their social secure payments might be reduced.