See post #540...They have the right to challenge the laws and see what the state comes up with for a legitimate state interest being furthered in the restriction on how many legal spouses they can have. In all likelihood though the state can show at least a legitimate state interest is furthered in some way by restrictions on how many spouses any person in the US can have. It doesn't take much. The problem with restrictions on marriage based on sex/gender is that there are no legitimate state interests being furthered. It is still just two people, so there is no conflict within the laws based on that (whereas, with a person having more than one spouse, there is a conflict). No one is harmed (which can be shown to happen in some cases of polygamy, but can't really be shown in all so not really a good argument pertaining to multiple spouse restrictions). And marriage laws are gender-neutral (which still wouldn't pertain to multiple spouses, but marriage laws are not number of spouses neutral in their operation).