What is the test for a habeas corpus challenge to individual parole denials?

^9. Various claims of systemic bias in California's parole process have been raised in vain in the habeas corpus context over the years. Even before Swarthout categorically foreclosed habeas challenges to individual parole denials, the AEDPA's limits on relief and the anti-retroactivity rule of Teague v. Lane, 489 U.S. 288 (1989), prevented relief on any constitutional theory not already established by precedent. No such limitations affect the court's analysis here.