In summary, considering that the Supreme Court has delegated to the states the responsibility of developing appropriate ways to enforce the constitutional restriction against executing mentally retarded defendants, we cannot second-guess the decision of the Court of Criminal Appeals. Were the court to hold that the decision of the Court of Criminal Appeals was an unreasonable application of federal law under Atkins, we would be requiring the state court to substantially alter its established rule despite the Supreme Court’s delegation of such rulemaking to the state. This is precisely what a federal court reviewing a state court decision under AEDPA’s deferential standard cannot do in the absence of an unreasonable application of a clearly established federal law as defined by the Supreme Court.
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