In case people didn't realize what the argument before the court today will be about. A widow (her wife died, she was legally married in Canada) is being forced to pay $400,000 + in Estate taxes, which would never happen to a male/female marriage. I'm guessing there's a form of discrimination there somewhere, the only phrase that comes to mind is Homer Simpson D'oh.
Because Federal Government paperwork references "marriage" it does not reference Civil Union having one title for one group and another title for another group wouldn't work. Also there are many states that do not have Civil Unions point blank, and trust me there are a large group of people who do not want Civil Unions, many New Yorkers for example.