ruling on a coram nobis petition. Neither the 28 U.S.C. § 1651(a) statute making the writ of coram nobis available in federal courts in criminal matters nor any Federal Rule of Appellate Procedure requires a certificate of appealability before an appeal may be taken, nor does such a requirement appear in the case law. Some prisoners have attempted to file coram nobis petitions if AEDPA prevents the petitioner from filing under § 2255. However, federal courts have consistently held that prisoners may not resort to the writ of coram nobis in order to bypass AEDPA's gatekeeping requirements. The standard of review from a district court's denial of a coram nobis petition is similar to the standard of review from a district court's denial of a habeas corpus petition. Generally, the standard of review is that any district court's determinations on questions of law are reviewed de novo, but that district court's determinations on questions of fact are reviewed for clear error (or clearly erroneous error). Under de novo review of federal coram nobis cases, the appellate court acts as if it were considering the question of law for the first time, affording no deference to the decision of the district court. Under Clear Error review of federal coram nobis cases, the appellate court must have a "definite and firm conviction that a mistake has been committed" by the district court. U.S. state courts Only sixteen state courts and District of Columbia courts recognize the availability of writs of coram nobis or coram vobis. Each state is free to operate its own coram nobis procedures independent of other state courts as well as the federal court system. The writ of coram nobis is not available in a majority of states because those states have enacted uniform post-conviction acts that provide a streamlined, single remedy for obtaining relief from a judgment of conviction, and that remedy is available to petitioners who are no longer in custody. States that have replaced writs of coram nobis with remedies within their post-conviction proceedings are also independent of other state courts as well as the federal court system. These proceedings enacted by state legislatures may either be more or less stringent than the writs it replaced or the post-conviction proceedings of other states. Availability The following table provides whether each state's courts are authorized to issue a writ of coram nobis (or a writ of coram