Greek sprinter Katerina Thanou has threatened to sue IOC president Jacques Rogge personally if she is not allowed to compete at the Olympics.
Thanou is in Greece's squad, but Rogge has said he could bar her following her withdrawal from the 2004 Games.
In a letter obtained by BBC Sport, Thanou's lawyer warns the IOC he will take legal action if this happens.
"These actions will be directed not only against the IOC, but against certain IOC individuals," it reads.
Thanou and compatriot Kostas Kenteris missed a drugs test of the eve of the Athens Olympics.
It was the third time each had missed a test, resulting in an automatic two-year ban from competition by the IAAF.
The sprinters are also currently the subject of a criminal case after claiming to have been involved in a motorcycle accident in Athens on the evening of the missed test.
Read the letters in full
Rogge has already warned he will be able to prevent Thanou from competing at the Beijing Games, after she handed over her accreditation when asked to appear before a 2004 IOC disciplinary commission investigating her missed test.
"When Thanou handed over her accreditation, she was no more an Olympic athlete," Rogge said.
"We said at the time that we would review the eligibility of Thanou for Beijing."
The 33-year-old is also demanding to be awarded Marion Jones' 100m gold from the 2000 Olympics by Monday.
Failure to do so will also result in legal action, according to the letter obtained by BBC Sport.
"The IOC must hand the gold medal from the Sydney Olympiad to Ms Thanou... there are no legal grounds for refusing the medal," the letter reads.
The IOC is reluctant to award Thanou the gold medal, even though she finished second behind Jones in the Sydney 100m.
The IOC's executive board is due to discuss Thanou's case this weekend, by which time it will have received recommendations from the disciplinary commission.
Jones was stripped of her five medals from the Sydney Games after admitting she was taking the banned steroid THG at the time.
"When Thanou handed over her accreditation, she was no more an Olympic athlete"The IOC's director of legal affairs, Howard Stupp, sent a letter to Thanou on 25 July to outline the organisation's case against the sprinter.
This letter has also been obtained by BBC Sport and explains that the IOC will consider the following facts about Thanou's case:
• your general attitude and behaviour towards the IOC and the Olympic Movement (at) the 2004 Olympic Games
• your subsequent acknowledgement of having breached the rules of the IAAF
• the status of the criminal procedure directed against you by the Greek judicial authorities
A spokesman for the IOC said an announcement about Thanou was not expected before the end of next week.
Thanou held a news conference in Athens on Friday and held aloft her accreditation for the Beijing Games.
She said: "There is no official charge against me, so why am I being asked if I want to take part in the Olympics even though I have qualified under the rules?
"I have been maligned and my career was damaged... this is still going on. Enough is enough."
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