In the case of Mario Claiborne v. United States, 2006, the U.S. Supreme Court was asked to consider whether a sentence that significantly deviates from federal guidelines can be considered reasonable if it is based on factors already taken into account by those guidelines. The defendant, Mario Claiborne, had been convicted for possession of a small amount of crack cocaine and sentenced to 15 months in prison - considerably less than the recommended minimum under federal sentencing guidelines. The Eighth Circuit Court reversed this decision stating that such an extraordinary reduction must be supported by extraordinary circumstances. However, before the Supreme Court could make its ruling on whether or not such deviation from guideline sentences were permissible or should be deemed unreasonable per se (inherently), Mr.Claiborne passed away and his case became moot leading to dismissal without resolution.

In the dissenting opinion for Mario Claiborne v. United States, Justice Samuel Alito argued that the majority's decision to vacate and remand was premature and unnecessary. He contended that there was no clear error in the original sentencing by District Judge Limbaugh who had already considered all relevant factors under 18 U.S.C §3553(a) before deciding on a sentence below the advisory Guidelines range. Justice Alito emphasized that it is not within Supreme Court’s purview to second-guess district court judges' individualized sentencing decisions unless they are unreasonable or procedurally incorrect. Furthermore, he expressed concern over potential implications of this ruling which might encourage unwarranted disparities among defendants with similar records found guilty of similar conduct - something Sentencing Reform Act sought to avoid.