Double-amputee sprinter Oscar Pistorius has won an appeal to compete for a place in the Beijing Olympics.
In January, athletics' governing body the IAAF banned the 21-year-old South African from able-bodied events.
It was claimed Pistorius' prosthetic limbs give him an unfair advantage, but he disagreed and went to the Court of Arbitration for Sport (Cas).
"We have an opportunity to chase my dream of participating in the Olympics - if not in 2008 in 2012," he said.
"It is such a significant day in the sport - I'm so happy with the outcome. the last few days have been very stressful. this is one of the best days of life.
"I hope this silences the crazy theories circulating about my having an unfair advantage."
Cas said in a statement that the IAAF had not proved competition rules had been contravened.
"On the basis of the evidence brought by the experts called by both parties, the panel was not persuaded that there was sufficient evidence of any metabolic advantage in favour of the double amputee using the Cheetah Flex-Foot," the statement said.
The panel emphasised that their verdict only applied to the individual case of the South African.
It was also stressed that any advancements in the prosthetic-limb technology used by Pistorius could be contested by the IAAF again.
"The panel does not exclude the possibility that, with future advances in scientific knowledge, and a testing regime designed and carried out to the satisfaction of both parties, the IAAF might in future be in a position to prove that the existing Cheetah Flex-Foot model provides Oscar Pistorius with an advantage over other athletes."
Pistorius is hoping to make the Olympic 'A' standard time of 45.55 seconds for the 400m or the 'B' qualifier of 45.95 if no other athlete from his country attains the higher one.
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His best time over the distance in 2007 was 46.56 and his personal best is 46.46.
"There are some good South African runners over that distance and every national federation is allowed to take three athletes in an event provided they meet an 'A' standard and only one athlete if they can only meet the 'B' standard," said BBC Radio 5 Live athletics correspondent Mike Costello.
"At this stage Oscar Pistorius has only an outside chance of making that time.
"But now, with the impetus, with the incentive of the Olympic Games, if he can get invites to the big meetings around the summer, then maybe, with the conditions right, he can be dragged through to an even quicker time for what would be a landmark appearance at the Olympics.
"No other leg amputee has ever managed to compete at the Olympic Games."
The South African was born without fibulas - the long, thin outer bone between the knee and ankle - and was 11 months old when his legs were amputated below the knee.
He began running competitively four years ago to treat a rugby injury, and nine months later won the 200m at the 2004 Paralympic Games in Athens. Nicknamed the "Blade Runner," Pistorius has set world records in the 100m, 200m and 400m in Paralympic events.
He finished second in the 400m at the South African national championships last year against able-bodied runners.
Pistorius added: "My focus throughout this appeal has been to ensure that disabled athletes be given the chance to compete and compete fairly with able-bodied athletes.
"I look forward to continuing my quest to qualify for the Olympics."
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