The tricky thing is that, unlike issues of Substantive Due Process, which Scalia holds does not exist (and Alito, Roberts and Thomas have been heavily influenced by him and adhere to his position), this is a question of actual Due Process. As a result, it is possible, though not likely, that one of the four conservative justices could actually side with a majority in a qualified opinion supporting the verdict only but with heavy dicta that no decision is being made that civil union laws would need to be replaced with marriage laws.

The reason for this is that the Ninth Circuit judges seemed to really grasp, for once, that they are a laughingstock because of their overly liberal interpretations, and that if they wanted to actually make the situation of homosexuals in California better, rather than worse, they would have to really produce a thorough opinion that would lay the groundwork for a successful appeal.

I think that anyone who attempts to compare this case to Lawrence v. Texas is going in completely the wrong direction, however. The question there was privacy, and here it is a direct equal rights issue.