Habeas: Federal habeas corpus review: "second-guess the reasonable decisions of state courts", "clearly established Federal law": in this habeas case, the United States Court of Appeals for the Sixth Circuit set aside two 29-year-old murder convictions based on the flimsiest of rationales. The court’s decision is a textbook example of what the Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA) proscribes: “using federal habeas corpus review as a vehicle to second-guess the reasonable decisions of state courts.” Renico v. Lett, 559 U. S. ___, ___ (2010) (slip op., at 12). We therefore grant the petition for certiorari and reverse; as we explained in correcting an identical error by the Sixth Circuit two Terms ago, see Renico, 559 U. S., at ___ (slip op., at 11–12), circuit precedent does not constitute “clearly established Federal law, as determined by the Supreme Court,” 28 U. S. C. §2254(d)(1). It therefore cannot form the basis for habeas relief under AEDPA. Nor can the Sixth Circuit’s reliance on its own precedents be defended in this case on the ground that they merely reflect what has been “clearly established” by our cases (U.S.S.Ct., 11.06.12, Parker v. Matthews, Per Curiam).