To be clear: the way states who struggled to stop polygamy chose to fight it was by making living with more than two adults in a house illegal. That was struck down in federal court like twenty years ago or something. You can't legally keep consenting adults from forming whatever private unions they wish to form, from living with each other, sleeping with each other, etc., even if you can disqualify them from obtaining legal marriage certificates for more than one spouse. This isn't really a story. Polygamy has basically always been simultaneously legal and illegal depending on how you look at it, and I'm fine with that.