Park has already served an 18-month ban imposed by swimming's world governing body FINA but is fighting to repeal a KOC regulation that imposed an additional three-year suspension, effectively ruling him out of the Rio Olympics.
The KOC said last week it had turned down Park's appeal to overturn the suspension, leaving the swimmer's hopes of competing at Rio in the hands of the CAS.
Sean Lim, an attorney with the Lee & Ko law firm representing Park, said at a news conference in Seoul that the swimmer would lodge an injunction against the KOC and Korea Swimming Federation later on Thursday.
"Park is filing for injunction in Eastern Seoul district court today right after the briefing," Lim said. "This is to prepare for the situation where the KOC refuses to comply with the CAS decision."
Lim added that they expected CAS to rule by July 5.
MORALITY
Given Park's profile in Korea, and amid criticism that the KOC regulation punishes an athlete twice for the same offence, speculation grew that it may relax the rule to give the swimmer the chance to compete at the Rio Olympics.
However, the KOC have shown no sign of easing its hardline stance on doping, saying that national athletes were required to show a "high level of morality" and that they were taking a stand for the sake of the country's young athletes.
Despite the KOC ban, Park entered national swimming trials in April and won all four of his races in times quick enough for Olympic qualification.
At the 2008 Beijing Games, Park became the first Korean to win an Olympic swimming medal when he took gold in the 400 metres freestyle. He also picked up a silver in the 200 in Beijing, and was runner-up in both races in London in 2012.
His Olympic exploits made him one of Korea's most popular, and highest paid, athletes but his clean-cut image was shattered when it emerged he had tested positive for testosterone ahead of the 2014 Incheon Asian Games.
Park, who attributed the failed test to an injection he received at a local clinic where he said he was being treated for a skin complaint, is currently training in Australia.
(Reporting by Jeongeun Lee; Writing by Peter Rutherford; Editing by Sudipto Ganguly)
