It was so low-key that it was almost subterranean, but Dwain Chambers's 100 metres comeback was good enough to initiate a landmark legal wrangle and prompt the disgraced sprinter to talk of winning a medal at the Olympic Games this summer.

Chambers ran 10.25sec into a strong headwind at the Papaflessia meeting in the Greek city of Kalamata, which was easily fast enough to ensure that he will compete at the Olympic trials in Birmingham next month. By then he hopes to have defeated the British Olympic Association (BOA) bylaw that prevents doping offenders from appearing on sport's biggest stage. Nick Collins, his lawyer, confirmed that the paperwork is in place and that they would be challenging the legality of the BOA rule next week.

The distraction could lead to huge embarrassment if Chambers wins his High Court battle, triumphs at the trials and makes good on his Olympic prediction. “I don't want to put my country in a difficult position and I'm doing this because I believe I can win a medal in Beijing,” Chambers said.

That is quite a comment, given that Chambers has run little since leaving the sport after the European Championships in 2006. His best time there was 10.24, good enough for fifth in the final but pedestrian by modern standards. However, he looked in superb shape when taking a share of the 60 metres silver medal at the World Indoor Championships in March and backed that up by winning yesterday, beating Mardy Scales, of the United States, who has run 10.07.

Significantly, Chambers believes that he has a future in the sport. Although Euromeetings, the umbrella group representing most of Europe's leading promoters, has advised its members to snub drug offenders, Chambers has been invited to a low-key meeting in Germany this month. Collins said: “His trial at Castleford rugby league club showed that people will pay to come and watch Dwain perform.”

The BOA has vowed to defend vigorously its position, but Dick Pound, the former president of the World Anti-Doping Agency and a lawyer, said that the association is on “shaky ground”, while Adrian Barr-Smith, of Denton Wilde Sapte, a leading sports law firm, said that the more lenient “banning regimes” of other sports would be taken into account.