High-speed rail opponents are appealing to California's Supreme Court.

A group of Central Valley residents want justices to overturn a lower court ruling that allowed the $68 billion project to proceed, saying it undercut nearly a century of precedent that the state strictly comply with promises made in ballot measures.

Proposition 1A, authorizing bond sales, promised that officials would identify funding before starting construction on an initial stretch, but the opponents say they only found $6 billion of the $26 billion needed.

A new plan was ordered, then overturned.

It's not clear whether the high court will take up the new petition.