When will a district court's determination that the Current Petition is barred by section 2244(b)(1) of the US Constitution be considered to be a successive or successive habeas corpus application?

Pursuant to 28 U.S.C. 2244(b)(1), "[a] claim presented in a second or successive habeas corpus application under section 2254 that was presented in a prior application shall be dismissed." In challenging the district court's determination that the Current Petition is barred by section 2244(b)(1), Henderson makes two primary arguments. First, he contends that the Current Petition should not be treated as successive because the district court did not reach the merits of the claims in the First Petition. Second, he argues that even if a dismissal on grounds of state procedural default renders a later petition successive, we should consider the First Petition as having been dismissed as unexhausted in deciding whether the Current Petition is successive. He points out that the district court addressing the First Petition was unaware that the Resentencing Appeal was still pending at the time the First Petition was filed, and he argues that the First Petition should have been dismissed as unexhausted rather than procedurally defaulted because he (supposedly) still had state remedies available. His argument continues that if the First Petition had in fact been dismissed as unexhausted, section 2244(b)(1) would not bar the Current Petition, because "[a] habeas petition filed in the district court after an initial habeas petition was unadjudicated on its merits and dismissed for failure to exhaust state remedies is not a second or successive petition." Slack v. McDaniel, 529 U.S. 473, 485-86, 120 S.Ct. 1595, 146 L.Ed.2d 542 (2000).