[QUOTE=Canadjun]
This is pure hypothesizing on my part - I am not a lawyer in any jurisdiction. However, to my way of thinking, it would be extremely difficult to prosecute polygamy unless someone is foolish enough (and yes, I know some are!
) to actually get multiple marriage licenses. I don’t think members of that fundamentalist mormon sect that is still into polygyny actually get multiple marriage licenses - from the viewpoint of their beliefs the husband has multiple wives, but from a legal point of view he is simply being rather open about practicing adultery, which isn’t illegal.
[/QUOTE]
No, it’s illegal. It was recognized that the defense of “I’m not LEGALLY married to any of these other wives!” would be used by everybody (except the traditional folks that were prosecuted as bigamists – the ones who deceived both wives [or all of them, if there were more than two] into thinking they were the sole legal wife … but that doesn’t really apply to Mormon-style polygyny, where all the wives know what’s up), since technically you can’t legally marry more than one woman. If they admitted that the polygamists were just open adulterers from a legal standpoint, they’d have a hard time prosecuting Mormon polygamists (and achieving the ultimate goal of suppressing the practice of polygamy) without being accused of selective prosecution for not prosecuting “normal” adulterers too.
So the anti-polygamy laws were crafted to make plain ol’ “bigamous cohabitation” illegal – “bigamous cohabitation” being essentially the situation we’re discussing, where a man and multiple women act like they’re husband and wives (i.e., have sex and probably children together).
I’d produce a cite for the actual laws – in the western states where this kind of thing is common, at least, such as Utah, Arizona, Idaho, Wyoming, etc. – but I’m almost dead with exhaustion at the moment. Hopefully somebody else will do so while I’m asleep, thus freeing me of all responsibility. 
Also, sugar and spice, Tom Green was not a member of the FLDS church (Fundamentalist Church of Jesus Christ of Latter-day Saints). As far as I know, he was his own brand of Mormon fundamentalist. The FLDS were the cult based in Colorado City and who looted the local school district’s funds and fled to Texas, and whose prophet Warren Jeffs was recently placed on the FBI’s Ten Most Wanted list and who was caught.
Not that there’s much of a difference – they’re both pretty evil, assuming you consider child abuse and sexual coercion evil.