Why is it illegal to have multiple spouses?

[FrustratedFool]

That doesn't seem a big enough risk without other ways to counter it so as to have a blanket prohibition on what is effectively a basic human right (to marry who one wants and have a family life of one's choosing).

Surely we don't limit basic human rights without really good justifications and once other solutions to problems have been exhausted.

I mean, if we allow guns and intoxicants and porn and brothels and casinos and cars and etc with all those risks ...