In this en banc opinion, the Ninth Circuit reversed the district court’s dismissal of the habeas petition and remanded for further proceedings to determine whether the petition was “time-barred.” Petitioner advanced two theories: equitable tolling and the existence of an “impediment” to the timely filing of his federal habeas petition. Each theory was predicated on the unavailability of material concerning the Antiterrorism and Effective Death Penalty Act in the prison library. The matter was remanded with instructions to the district court to develop the facts and assess their legal significance, because the Ninth Circuit disagreed with the district court’s conclusion that there are no circumstances, consistent with petitioner’s petition, that would entitle petitioner to a finding of an impediment or grounds for equitable tolling.