The Marijuana Misdemeanor Expungement Act would automatically erase federal criminal records for low-level marijuana offenses and allow individuals to petition courts to expunge their marijuana-related records. The bill applies to federal misdemeanors, petty offenses, infractions, and civil penalties involving marijuana but excludes felony convictions and unrelated offenses. Within two years of enactment, federal district courts would conduct a comprehensive review and expunge eligible records, while individuals could also file petitions for expungement at any time after the law takes effect. Once expunged, individuals can legally deny that the arrest or conviction ever occurred, and the offense cannot disqualify them from jobs or professions. The Government Accountability Office would be required to conduct a study of federal marijuana-related prosecutions and report findings to Congress within two years, with implementation details to be established by the Chief Justice of the United States within one year of the law's passage.