In the Sumner v. Mata case of 1980, the U.S Supreme Court ruled that federal courts must give deference to state court decisions on issues of fact unless there is clear and convincing evidence that they are erroneous. The petitioner, a warden at San Quentin State Prison in California, appealed a decision by the Ninth Circuit Court of Appeals which had granted habeas corpus relief to respondent Mata based on his claim that he was denied effective assistance of counsel during his trial for murder in state court. The Supreme Court held that under Section 2254(d) of Title 28 - Procedure and Evidence Act (1966), it was not enough for federal courts to simply disagree with findings made by state courts; rather, they needed compelling proof showing these findings were incorrect or unreasonable based on evidence presented during trial at the state level. This ruling reinforced respect for states' rights within our federal system while also ensuring fair treatment for defendants.

In the dissenting opinion for Sumner, Warden v. Mata (1980), Justice William Rehnquist argued that federal courts should not have the power to overturn state court decisions unless there is a clear violation of constitutional rights. He believed that the majority's decision undermined states' authority and autonomy in their own legal proceedings by allowing federal courts to reevaluate factual determinations made by state courts. According to him, this was contrary to Section 2254(d) of Title 28 which limits federal habeas corpus review over state convictions. He contended that such reviews should only be conducted when it can be shown beyond reasonable doubt that a constitutional error has occurred, rather than simply because a different interpretation could potentially lead to another outcome.