In the case of Jason Pepper v. United States (2010), the U.S. Supreme Court ruled that when resentencing a defendant, a court may consider evidence of the defendant's post-sentencing rehabilitation and that such consideration does not violate federal sentencing guidelines. The case involved Jason Pepper who had been convicted on drug charges and initially sentenced to 24 months in prison but was later resentenced to 77 months after several appeals by both parties. During this time, Pepper had made significant strides in rehabilitating himself which were considered during his final sentencing hearing - an action challenged by the government as being contrary to federal law. However, Justice Sonia Sotomayor delivered the opinion for a majority court stating that district courts have long taken into account information about defendants' backgrounds, characters and conducts including their post-sentence conduct at re-sentencing hearings.

In the dissenting opinion for Jason Pepper v. United States, Justice Clarence Thomas argued that federal sentencing guidelines should be followed more strictly. He disagreed with the majority's decision to allow judges to consider post-sentencing rehabilitation when resentencing a defendant after an appeal. According to him, this approach undermines the predictability and consistency of sentences which are key goals of the Sentencing Reform Act (SRA). Furthermore, he contended that considering post-sentencing behavior could lead to unfair disparities in sentencing because it would favor defendants who have resources or opportunities for rehabilitation over those who do not. Lastly, he expressed concern about potential violations of separation-of-powers principles if courts were allowed too much discretion in determining sentences.