Everyone has probably heard that the California Supreme Court has backed Proposition 8 which was a referendum held at the time of the US Presidential Election and which incorporated into the California Constitution a legal definition of Marriage as being between a Man and a Woman. The passing of Proposition 8 has stopped same sex marriages being performed in California.
Without going into the merits of all the arguments about same sex relationships i thought the following two legal points might be of interest.
The Mormon Church has been heavily criticised by gay rights activists over its support for monogamous heterosexual marriage but it is worth remembering that in the 19th Century Mormons were themselves forced to accept this legal definition of Marriage or face imprisonment, see Reynolds v. U.S., 98 U.S. 145 (1878). Mormons practiced Polygamous (or plural) marriage which was a requirement of their religion. In response to this action by the Mormon Church Polygamy was outlawed by the US Government which stated that only monogamous marriage could have legal status and the US Supreme Court defended this legal ban on polygamous marriage by reference to the historic understanding of marriage in western society. There is an argument, which is already being pursued in Canada, that if the historic definition of marriage as one man and one woman is no longer legally valid then laws against polygamy are similarly legally invalid.
Also it is worth noting that the argument is solely over the term "marriage" Californian law already permits Same Sex "Domestic Partnerships" which are basically the same as Marriage but without the name. In the UK we adopted the same approach with Civil Partnerships so Britain is neither better, nor worse, than California (except of course for being rather wetter)