Considering the Proposition itself is a state constitutional amendment, it would seem that the Proposition can only be disqualified on procedural/technical grounds.
However, and this is a somewhat perverse approach, but let's consider two sort of stipulations put in place, one by the courts, one by the Proposition.
A) Granting marital rights to mixed-sex couples and not to same-sex couples is unconstitutional.
B) Granting marital rights to same-sex couples is unconstitutional.
These two assumptions are not mutually exclusive. If Prop 8 is written like how B is written, and not as an explicit contradiction of A, then here is reasoning I can take:
p: The state can grant marital rights to mixed-sex couples.
q: The state can grant marital rights to same-sex couples.
A) (p AND ~q) = False, which holds if either p = False or q = True.
B) q = False
Statement B forces q to be False. In order for A to be true, p must also be False.
In other words, the state cannot grant marital rights to mixed-sex couples. The state courts should deny the legal status of marriage to EVERYONE. Unless there's explicit language in the Proposition affirming a right of marriage to mixed-sex couples (which *would* override the ruling), this conclusion must stand.
Now that would get the attention of these religious goons.