Is a state procedural rule that does not apply consistently enough to prevent a federal court from dismissing a second habeas petition?

We faced a similar problem in Siripongs v. Calderon, 35 F.3d 1308, 1318 (9th Cir.1994), where we held that the district court's dismissal of petitioner's claims in a successive habeas petition on procedural grounds was error. We ruled that a state procedural rule that is discretionary and not applied consistently "cannot act as a bar to federal review.... [T]he federal courts should not insist upon a petitioner, as a procedural prerequisite to obtaining federal relief, complying with a rule the state itself does not consistently enforce." Id.