Does a knowing and voluntary agreement to waive the right to appeal a sentence always remain enforceable? Specifically, does such a waiver preclude an appeal even if the resulting sentence is unconstitutional or otherwise egregious? Furthermore, does a trial court's misstatement regarding appeal rights at sentencing void a written appeal waiver?

Petitioner argued that an appeal waiver is unenforceable when the disputed aspect of a sentence violates a fundamental constitutional right. Alternatively, petitioner contended that the District Court’s representation at sentencing that he had a right to appeal voided the waiver. Petitioner further asserted that the prosecutor’s failure to object to the court's misstatement effectively waived the Government's right to enforce the agreement.

Respondent maintained that knowing and voluntary appeal waivers are always enforceable regardless of the sentence's nature. Respondent argued that the District Court's oral misstatement did not modify the written plea agreement, which required modifications to be in writing and signed. Respondent further contended that silence during the sentencing hearing did not constitute a waiver or forfeiture of the right to enforce the appeal waiver.

The Court held that an appeal waiver is unenforceable if its enforcement would result in a miscarriage of justice. This standard applies only when a sentence is marred by an obvious, egregious error that would undermine public confidence in the judiciary. The Court reasoned that the judiciary has an "independent" "institutional interest" in ensuring legal proceedings "appear fair to all who observe them," citing *Wheat v. United States*. It further noted that some rules are "so fundamental" that they cannot be waived "without irreparably discrediting the federal courts," invoking *United States v. Mezzanatto*. Because district courts use "sound judicial discretion" under *Santobello v. New York* to accept pleas, the judiciary is too enmeshed in the process to allow automatic enforcement of waivers that risk institutional harm. The Court rejected the idea that the District Court's oral misstatement modified the agreement, as the contract required modifications to be "in writing and signed by all parties." It also found that the Government did not forfeit its rights through silence, as the proper time to assert an appeal waiver is after a notice of appeal is filed, citing *Garza v. Idaho*. To guide lower courts, the Court identified three examples of errors that may constitute a miscarriage of justice. These include sentences exceeding the statutory maximum, sentences infected with blatant constitutional errors (such as those based on race), and sentences imposed without a "minimum of civilized procedure." The Court declined to decide if petitioner's specific medication condition met this bar, remanding the case to the Fifth Circuit.

Justice Thomas, writing alone, argued that the right to appeal is a mere statutory right under *18 U.S.C. § 3742* that can be knowingly and voluntarily waived. He contended that the majority created a "miscarriage-of-justice" exception based on policy concerns and public perception rather than a