The Antiterrorism and Effective Death Penalty Act of 1996 (AEDPA) further limited the use of the federal writ by imposing a one-year statute of limitations and dramatically increasing the federal judiciary's deference to decisions previously made in state court proceedings either on appeal or in a state court habeas corpus action. One of AEDPA's most controversial changes is the requirement that any constitutional right invoked to vacate a state court conviction rooted in a mistake of law by the state court must have "resulted in a decision that was contrary to, or involved an unreasonable application of, clearly established Federal law, "as determined by the Supreme Court of the United States"" (emphasis added). Thus, a U.S. Court of Appeals must ignore its own precedents and affirm a state court decision contrary to its precedents, if the U.S. Supreme Court has never squarely addressed a particular issue of federal law.