Chambers won silver at the 2008 world indoor championships
Dwain Chambers has won his first 100m race since August 2006 in a time that qualifies him for the British Olympic trials in Birmingham on 11 July.
The British sprinter, who has completed an IAAF two-year ban for testing positive for the steroid THG, clocked 10.26 seconds at Papaflessia in Greece.
And Chambers, 30, plans to challenge his lifetime ban by the British Olympic Association at London's High Court.
"Beijing is still there. I'll be there, don't worry," he said.
"I believe that I can be in the first three in Beijing. I can win a medal."
Chambers returned to the track in January and won a silver medal in the 60m at the world indoor championships in March.
Nick Collins, Chambers' Leeds-based solicitor, said that an appeal could take place in the High Court before the end of next week.
The BOA says it is confident its Olympic doping rule would stand up in court and have insisted they will oppose Chambers' reinstatement and defend their bylaw no matter what the financial cost will be.
Although there have been 26 successful appeals against Britain's lifetime Olympic ban in the last 16 years, the legality of the rule has not been challenged in the courts.
Controversial Londoner Chambers is now fully focussed on overturning his ban, having gone well under the 10.85 qualifying time required to take part in the British trials.
Mardy Scales of the United States had a better start in the final at the annual meet in Greece, but Chambers caught up and passed him just before the finish line.
"I was pleased just to be here, first and foremost, and get back into the swing of competition," he said.
"It was good to be performing today. I'm very happy."
Under BOA rules, athletes found guilty of drugs offences cannot represent GB at the Olympics.
As Chambers prepares to return to action, his former manager John Regis has said he should not be allowed to compete in Beijing in August.
"Dwain knew there was the rule set by the BOA that if you take steroids you can no longer participate in the Olympics," he said.
"The rule was in place before he decided to take steroids and I think it should stand.
"Those who cheat should have the full weight of the law thrown at them."
Chambers has switched his focus back to the track after failing in his pursuit of a rugby league career with Castleford.