Today the United States Supreme Court decided that the Supreme Court could not decide the constitutionality of Proposition 8 because the people bringing the case didn't have standing.
The state of California refused to defend the vote of the people in this case so supporters of Proposition 8 attempted to represent the case. The Supreme Court rejected this representation.
Justices ruling against standing:
Stephen Breyer, and Ruth Bader Ginsburg, Elena Kagan, John Roberts, and Antonin Scalia
Justices supporting standing:
Samuel Alito, Anthony Kennedy, Sonia Sotomayor, Clarence Thomas
The court ruling can be read here.