Our government is run by the Constitution. The constitution is how the people tell the governmen how to run it and the parameters of the laws it can pass with the peoples will.
Prop 22 in Calif was a change to the Constitution, not a law to be ruled on my the courts, it is actually the opposite. We told the government how to operate and what laws they can pass.
Yes; I'm curious how an amendment to the Constitution can be un-Constitutional. By definition, amendments are Constitutional as they are the Constitution.