If Utah make polygamy legal.

We have done this before. To quote myself from that thread:

I think is entirely possible to have a morally and ethically sound committed relationship with more than two partners. Being in such a relationship should not be a crime in and of itself. But to give that type of relationship the legal standing, protections, and presumptions of current two party marriage is certainly non-trivial (SSM only required pronoun changes for the most part), and may not be possible.

I will quote myself again on the complexity that must be addressed in any legal changes that recognize multi-party marriages:

Bottom line for me: If those who wish poly marriages can ever come together and agree with a proposal that would address all the legal ramifications I would not be opposed to it on principle. I may oppose a specific proposal or aspect of said proposal if it seems discriminatory (men can have multiple wives, but not vice versa or the power is vested in one sex over the other when it comes to divorce) or puts an undue burden on the 99% of the population that wants to be in a two party marriage (requiring a specific, detailed contract for every marriage). If those requirements are met I would support such laws at the national and state level. I just don’t see that happening anytime soon.