The proposition is not a referendum law, it's an amendment to the California State Constitution.
It was done that way to overrule the appelate court decision that overturned the original California referendum preventing queers "marrying" each other. Retro nomenclature and references intentional...
So the question really at issue is whether the SCOTUS has the jurisdiction to overturn an element of a State Constitution.
It's unprecedented to imagine that it does. The States are sovereign, and if the federal union doesn't like the State Constitution, it's a matter for Congress to debate, not the SCOTUS, because that was the body that accepted the State application for inclusion in the Union.
Courts don't have the right to re-write the founding documents of either the Union or the States of the Union.
To put it in clearer terms, do the Courts have the right to declare the Constitution Un-Constitutional?
I can think of nothing more absurd.
I do not remember which court started the practice, but Scotus has increasingly “incorporated” the US Bill of Rights and applied it to the States. It is a sh!tty subterfuge, because the sovereign people of CA approved prop 8 just as conventions of others ratified the US Constitution.
Thank the 17th Amendment. Since States could no longer defend themselves it effectively repealed the Ninth and Tenth. Once a dispassionate umpire, Scotus is part of the same ruling class as Congress and the Prez. Aside from calling a Constitutional Convention, there isn't a thing the States can do about it.