One case involves Defense of Marriage Act (DOMA), a federal law which was passed in 1996. This particular statute defines marriage solely between one man and one woman for federal and inter-state recognition purposes in the United States. Essentially, a same-sex couple married in Massachusetts (where such a union is legal) would not have their marriage license recognized in, say, North Carolina, where gay marriage is illegal. It also denies same-sex couples, who are legally married under state law, a significant amount of federal benefits afforded to a heterosexual married couple. It's likely DOMA gets overturned (and in my opinion, it should), as this deals solely with the contract side of marriage as opposed to the religious aspect.
On Tuesday, the oral arguments began over Proposition 8, the California ballot initiative which voters approved in November 2008, defining marriage as solely between one man and one woman. Last year, the Ninth
California is an interesting situation in that civil unions are legal there. With that being the case, it would appear the "Equal Protection" isn't as applicable here since every adult "union" already has the same financial benefits, an issue which seems to be the crux of almost every argument concerning gay marriage.
As I've said recently on this blog, I believe gay marriage will one day be the universal law of the land. The current generation of adults under 30 seem to strongly support such an arrangement, so this will be an issue that will eventually be resolved electorally. But legalizing gay marriage via judicial fiat is not the wisest proposition, because that would seem to fly in the face of the "separation of powers" clause. To that point, I'm often perplexed at the myriad protests which take place outside the Supreme Court building whenever a landmark case is being adjudicated. Showing staunch support or opposition to same-sex marriage will have zero impact on the judicial branch (At least we better hope that's the case).
As far as predictions of how the decisions will be rendered, my guess is DOMA will be overturned but Prop 8 will be allowed to stand. The rationale behind this may be similar to the spirit in which Obamacare was upheld. That is, it should be left to our democratic processes to best determine our laws of the land.....provided said laws meet the Constitutional check of course.