Park Tae-Hwan has appealed to the Court of Arbitration for Sport (CAS) in an attempt to overturn a ban preventing the Korean swimmer from competing in the Rio Olympic Games.
The 26-year-old, who won Olympic gold in the 400-metre freestyle back in 2008, was last year given an 18-month suspension for testosterone back in 2014.
Park's period of ineligibility ended on March 2, but Korean Sport and Olympic Committee rules state that athletes are still unable to represent their country for three years after serving a ban for doping.
Seoul-born Park, a winner of two silver medals in the 2012 London Games and another in Beijing four years earlier, has refused to accept that ruling and opted to take his case to CAS.
A CAS statement said: "The Korean swimmer Tae Hwan Park has filed an appeal at the Court of Arbitration for Sport (CAS) against the Korean Sport and Olympic Committee (KOC) and the Korea Swimming Federation (KSF).
"Mr Park seeks an urgent ruling that would potentially allow him to compete at the Rio 2016 Olympic Games.
"In March 2015, the Federation Internationale de Natation (FINA) imposed an 18-month period of ineligibility on Tae Hwan Park following a positive anti-doping control for testosterone.
"His ban started on 3 September 2014 and ended on 2 March 2016. KOC regulations prohibit an athlete from competing for the Korean national team for three years after the completion of a doping sanction.
"Accordingly, the KOC has announced that it will not select Tae Hwan Park for the Rio 2016 Olympic Games.
"Tae Hwan Park is challenging such announcement before the CAS and seeks an urgent ruling by 8 July 2016, the cut-off date for selection to the Korean national swimming team for the Rio 2016 Olympic Games."