Can a waiver of attorney's conflict of interest be denied?

But waiver is not without its limits. Some rights are so fundamental to the reliability of the factfinding process that they may never be waived without irreparably discrediting the federal courts. United States v. Mezzanatto, 513 U.S. 196, 204, 115 S.Ct. 797, 130 L.Ed.2d 697 (1995) (internal quotation marks and brackets omitted). Courts have an independent interest

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in ensuring the fairness and integrity of the criminal process, both with respect to each individual defendant but also so that legal proceedings appear fair to all who observe them. Wheat v. United States, 486 U.S. 153, 160, 108 S.Ct. 1692, 100 L.Ed.2d 140 (1988) (holding that, for this reason, courts may refuse to accept defendant's waiver of attorney's conflict of interest).