OLSON: Well, you've said in the cases decided by this court that the polygamy issue, multiple marriages, raises questions about exploitation, abuse, patriarchy, issues with respect to taxes, inheritance, child custody, it is an entirely different thing. And if you—if a state prohibits polygamy, it's prohibiting conduct. If it prohibits gay and lesbian citizens from getting married, it is prohibiting their exercise of a right based upon their status.Amy Hall has some good thoughts about this (link), but I want to point something else out - actually three things, the first of which is:
When the government prohibits marriage to already-married people, it is prohibiting "exercise of a right" (assuming marriage is a right) based on their status of being married. It is prohibition that is explicitly based on the status of the person. In fact, if getting a marriage license were like getting a job, they wouldn't be allowed to ask if you were already married. Prohibition of polygamy is about status. That's my main point.
The second is much more nuanced. When two people of the same sex seek to be "married" to each other, they are not being prohibited from "exercise of a right" - even if marriage is a right - because they don't want marriage as that term is defined. They want something that isn't marriage, which they want to be called marriage and treated as marriage.
The third point is that calling marriage a "right" is odd, given that in America single people apparently don't have this right unless someone else voluntarily consents to it. Can you imagine if your right to free speech depended on the people hearing you consenting to it? I'm pretty sure the pro-abortion folks wouldn't think a woman has a "right to choose" if she has to get someone else (like whoever procreated with her or the child) to voluntarily consent.