An initiative's official proponents have a great interest in the validity of a successful measure, but a limited role in California's initiative process.Our law does not protect their post-adoption interest by giving proponents the authority to represent the state's interest against a challenge to the validity of a measure that has become state law. And our law does not afford official proponents any legal right, arising solely from their role as proponents, that is injured by a judgment invalidating a law adopted by initiative. Instead, once an initiative measure is approved by the voters, a court considering a challenge to the measure's validity may grant the measure's proponents leave to intervene and participate in its defense, or as amicus curiae, but only to represent their own interests as individuals, not those of the state.