No formal charges have been filed yet, but FINA -- the international governing body for swimming -- has filed an appeal to the Court of Arbitration for Sport to "clarify issues surrounding this case."
Thorpe was not charged with a violation, but FINA took its own look at the test and determined it should have been reported as an "adverse" finding.
The 24-year-old Thorpe has retired from competition, but the test was conducted last May and was only made public this weekend by the French newspaper L'Equipe. The Washington Post said Australian swimming officials described Thorpe as shocked by the news.
Thorpe won five Olympic gold medals and 11 world championship titles in his career.