Dwain Chambers and David Millar have been given the all clear to compete at the London 2012 Olympics following a court ruling.
The Court of Arbitration for Sport (CAS) has declared the British Olympic Association's lifetime ban on drugs cheats invalid.
It has decided the ban is incompatible with the World Anti-Doping Agency's code and is therefore unenforceable.
It means cyclist Millar and sprinter Chambers, who have both admitted cheating with drugs, will be eligible to compete for Team GB at the Games.
They both received a two-year ban for their doping offences, Chambers in 2003 and Millar in 2004.
CAS said in a statement: "The by-law is a doping sanction and is therefore not in compliance with the WADA code.
"The CAS confirms the view of the WADA foundation board as indicated in its decision.
"Therefore, the appeal of BOA is rejected, and the decision of the WADA
foundation board is confirmed."
BOA chairman Lord Moynihan described the outcome as a "hollow victory for WADA" and said the body would be pushing for tougher sanctions for doping offences in the global code.
He also confirmed that Chambers and Millar were now free to be selected by their sports, and would be treated the same as all the other Team GB members if selected.
WADA president John Fahey welcomed the ruling but attacked the BOA for its behaviour during the case.
"The WADA decision was taken only after the full deliberation and consideration of independent legal advice and WADA regrets the many hysterical and inaccurate public statements from the BOA in the course of challenging the WADA decision," he said.
UK Athletics confirmed any athletes affected by the lifetime ban would now be eligible for selection.
It said in a statement: " UK Athletics has always supported the BOA by-law but welcomes the clarity the CAS decision brings to this issue.
"Athletes affected by the ruling are now eligible for the team, in both individual and relay events, and will be subject to the same selection criteria and process as every other British athlete."
Millar is likely to be part of the Olympic cycling team in London but British Cycling refused to speculate on the possibility.
A spokesperson said: "Our team for the Games is being selected in June and across all disciplines we'll pick the team based on which riders are fit and available, and who we believe have the best chance to deliver medals.
"Ahead of that we won't be speculating on who may or may not be selected."
Hugh Robertson, sports and Olympics minister, said the ruling was "disappointing" and called for tougher sanctions for doping offences.
He said: "I supported the BOA's position, as our national Olympic committee, in having the autonomy to set its own eligibility criteria for Team GB athletes.
"I accept this ruling from the Court of Arbitration for Sport but it is very disappointing.
"Moving forward, I fully endorse UK Anti-Doping's first submission to WADA as part of its review of the World Anti-Doping Code. I want the code to be further strengthened and I would particularly like to see tougher sanctions for proven drug cheats.
"The UK takes its responsibilities in the fight against doping in sport seriously.
"As we host the Olympic and Paralympic Games this year, we are promoting this message through the international Win Clean campaign."
Prior to this case, British athletes who were found guilty of doping were subjected by the BOA to a lifetime ban from the Olympics. This differed from other countries' approach to drug cheats and the case was taken to CAS for a ruling.
The BOA had argued that its lifetime ban for drug cheats was a "selection policy" and not a double sanction for cheats.
In November, in a case brought by American athlete LaShawn Merritt, CAS ruled that the International Olympic Committee's 'rule 45' which banned all athletes worldwide from an Olympic Games was illegal.
The latest decision appears to have backed up that ruling.
Following the news, British Hurdler Andy Turner tweeted: "Either make a lifetime ban for drug cheats worldwide or scrap it completely.
"The world won't follow Britain's rules so I'm happy for Dwain. I know my opinion will annoy people but I don't care. I see convicted drug cheats on the world stage all the time."