In 2000, California voters passed Prop. 22, which stated that California would only recognize opposite-sex marriages. In May, 2008, the California Supreme Court invalidated Prop. 22 as being in conflict with the California Constitution. In response, in November, 2008, California voters enacted Prop. 8, which amended the California Constitution to add that "only marriage between a man and a woman is valid or recognized in California." In May, 2009, the California Supreme Court upheld the Constitutional Amendment essentially banning same-sex marriages.
Fast forward to today. In response to the May, 2009 ruling, same-sex marriage proponents filed a lawsuit in Federal Court, alleging that Prop. 8 violated the federal civil rights of two same-sex couples that wanted to get "married". That case went to trial, and as you have undoubtedly heard, the Plaintiffs (proponents of same-sex marriage) won in a landslide. After hearing testimony from numerous witnesses, Judge Vaughn Walker struck down Prop. 8 as being in conflict with the Due Process and Equal Protection Clauses of the United States Constitution (see the next article for a very brief explanation of these clauses).
The decision came as a shock to noone, based on the evidence presented at trial. The Plaintiffs called reliable and persuasive witnesses (17 of them) who testified on all the benefits and the lack of societal detriment of same-sex marriages. On the other hand, the Defendants called unreliable and unpersuasive witnesses (and only 2 of them), whose testimony actually ended up helping the Plaintiffs. Ultimately, the Judge ruled that Prop. 8 could not stand up to strict scrutiny (or even the lesser standard of"rationally related") and struck down the Constitutional amendment.
So where are we now? As it stands today, same-sex marriages will be valid and recognized in California, pending any stays put into effect during the appellate process. Opponents of same-sex marriage will appeal to the 9th Circuit Court of Appeals, probably based on a "federalism" or 10th Amendment argument, i.e., the federal government cannot and should not decide an issue that is regarded as being within the exclusive province of the state in essence meaning, "this is a state issue, not a federal issue, and the state voters have spoken". Whichever side loses in the 9th Circuit Court will undoubtedly appeal to the United States Supreme Court, the ultimate authority, and absent an amendment to the United States Constitution, we should eventually have a final decision on the matter, one way or another.