I understand that the litigants attacking the law wouldn't want to rely on the Romer v. Evans doctrine in federal court, because that would eventually lead to a hostile SCOTUS. I also understand why they wouldn't rely on Romer alone, as the discriminatory proposition in that case (barring local governments in Colorado from passing anti-discrimination measures protecting gays) may well be distinguishable from Prop 8 — though I think a colorable comparison to Romer exists.

But why not assert that the California courts should recognize a Romer doctrine under the equal protection clause of California's own constitution? That could achieve the same result without triggering SCOTUS review. This California Supreme Court might well accept a doctrine that the California constitution prevents the populace from passing propositions divesting identified groups of previously recognized rights.