As usual, this is for general info purposes and is not intended a legal advice.
Hawaii: Okay, Hawaii is a damn good place to be polyamorous. It has no laws against fornication, adultery or cohabitation. There is also no specific law on the book against bigamy.
The law does specify that a marriage license will only be granted to a person who is not already married, so getting legally married to a second person would require lying when filling out a government form. I’m not sure what the technical offense would be, but my sources say it will earn you 30 days in jail. However, as long as you don’t apply for a marriage license under false pretenses and don’t get legally married to a second person, you can live together, have a religious wedding ceremony, have sex with whoever, and generally have your relationship in any configuration, living arrangement, or poly snuggle any way you like.
Idaho: Bigamy is punishable by a fine of at least $2000 and/or jail time that may be up to 3 years. Adultery is also against the law, though fornication is not. Idaho used to recognize common law marriages, it now recognizes common law marriages formed before 1996 but will not recognize new ones. As far as I can find it does not have laws against cohabitation.
In Idaho you are okay to be poly as long as you don’t get married. Throw marriage in the mix with poly and you are in violation of the adultery statute (which like many such is almost never used) or the bigamy statute, which has flexible requirements for proving that a second marriage took place: “Upon a trial for bigamy, it is not necessary to prove either of the marriages by the register, certificate, or other record evidence thereof, but the same may be proved by such evidence as is admissible to prove a marriage in other cases” – whatever that means.
Illinois: Adultery and fornication are both illegal in Illinois, but only if they are ‘open and notorious’. Illinois does not have a specific law against cohabitation, but only because if you cohabit while married you are guilty of bigamy whether or not there was ever a second ceremony. Illinois considers bigamy to be a felony.
Given the rarity of fornication prosecutions, you are probably alright in Illinois if you live together and are not married to anyone. If you are married and are poly but only live with your marriage partner you will probably be alright as long as everyone is happy with the arrangement – while they can prosecute for adultery whether or not the spouse was in agreement with the relationship it probably won’t be an issue unless you end up in divorce court. Being married with one poly partner and living with a second poly partner opens you up to bigamy charges. As said regarding other states, you can probably fly under the radar and be alright but if you come to official notice there may be problems.
Indiana: One of the simplest bigamy laws so far, Indiana sums it all up in two sentences. If you are married, and marry against you are guilty of bigamy. Unless you though your marriage was legal over due to death or divorce. Bigamy is a felony in Indiana. Indiana has no law against fornication or cohabitation, and does not recognize common law marriage. It does have laws against adultery but they only come into play if your spouse charges you with adultery.
Basically as long you don’t try to legally marry two people, and everyone is happy with the arrangement, you can do poly anyway you like in Indiana.
Iowa: Iowa classes bigamy as a ‘serious misdemeanor’ which comes into play if a person marries more than one person. Since Iowa recognizes common law marriage, this can get complicated. If you live together, imply and/or intend that you are married, and present yourselves as married (refer to each other as husband and wife [or husband and husband, etc] – the gold standard for ‘presenting yourselves as married’ is filing joint tax returns.) you can be in a common law marriage, which may end up with a bigamy charge if you are already married, under common law or otherwise, to someone else. Iowa has laws against adultery, but they are not currently enforced and will only be an issue in the case of a divorce. There are no laws against fornication.
So, as long as you do not present yourselves as married, and are not in danger of ending up in divorce court, you can live together, live separately, opening be in relations with and generally have lots of fun with your ply partners. Just be very careful about not ending up in a common law marriage if you are already married.
(As a side note, the legalization of gay marriage in Iowa opens some problems regarding common law marriage, as some gay and lesbian couples may be legally married under common law without realizing it.)
Kansas: Bigamy is a felony in Kansas, which comes into play when a person marries a second person. Period, no curlicues. Common law marriage is recognized in Kansas. You cannot end up in a common law marriage if you are already married, regardless of living together, intent, presenting yourself as married or anything else, so there is no chance of unintentionally ending up in a bigamous relationship because you live with two poly partners or someone you are not married to. Kansas also has laws against adultery that only come into play in a divorce. There are no laws against cohabitation or fornication.
Generally, polyamory will not cause problems in Kansas as long as any legally married spouse is happy with the arrangements and you aren’t trying to get two legal marriages.
Kentucky: If you marry or claim to be married to a second person in Kentucky you are guilty of bigamy. Also, if you have married someone in another state and live with someone else in Kentucky you are guilty of bigamy whether you claim to be married to the second person or not. Kentucky does have laws against adultery, but no laws against fornication or cohabitation, and it does not recognize common law marriages.
Overall, if you are not married in Kentucky you can do pretty much anything you want, relationship-wise. If you are married as long as you don’t claim to married to two people and your legally married spouse is happy with the situation you are good. The kink in the works: if you and your spouse married outside of Kentucky, you cannot live with another poly partner without violating the anti-bigamy law.
Louisiana: The act of marrying a second spouse in Louisiana, or living with a second spouse you married elsewhere, both constitute bigamy and are illegal. Adultery is illegal but can only get you in trouble if your spouse objects. Fornication and cohabitation are perfectly legal.
So, don’t get married and you are good however, if you are married and your spouse is okay with polyamory and/or is also polyamorous, you are good however, if you to get legally married twice or you spouse does not agree with poly, or changes their mind at a later date, you may have problems.
Next up: US states M-P