Opponents of same-sex marriage have long argued that allowing such unions will lead to marriages among more than two people and between adults who are related. They're right.

It’s been a few weeks since the victories in the marriage cases at the Supreme Court, and maybe it’s time for the political left to own up to something.

You know those opponents of marriage equality who said government approval of same-sex marriage might erode bans on polygamous and incestuous marriages? They’re right. As a matter of constitutional rationale, there is indeed a slippery slope between recognizing same-sex marriages and allowing marriages among more than two people and between consenting adults who are related. If we don’t want to go there, we need to come up with distinctions that we have not yet articulated well.

The left is in this bind in part because our arguments for expanding the marriage right to same-sex couples have been so compelling. Marriage, we’ve said, is about defining one’s own family and consecrating a union based on love. We’ve voiced these arguments in constitutional terms, using claims arising from the doctrines of “fundamental rights” and equal protection. Fundamental-rights analysis says that marriage is for many a crucial element of human flourishing, or as the Court said almost fifty years ago “essential to the orderly pursuit of happiness.” Because it’s so important, government can restrict marriage only by showing a truly compelling justification. The equal protection argument is simply that the marriage right should not be taken away from groups unless the government has good reasons to exclude those groups.

What it boils down to is that when the government wants to exclude groups from something important like marriage, it has to show good reasons for the exclusion.


Ickiness

Greenfield is a liberal law professor that actually supports same sex marraige.