Brief synopsis:
California Supreme Court has ruled that the state government has no jurisdiction over the choice of partner in marriage. Some opponents of this decision initiated prop 8, which if passed would reverse the decision made by the court.
Well, functionally it would reverse the decision of the court, yes. What it actually does is amend the state constitution to define marriage as between one man and one woman.
Also, the court didn't exactly say that the state government has no jurisdiction over partner choice. They said that withholding the right to marry from same-sex couples violated their state constitutional rights.
Not to be picky or anything.