Studies have proven that he spends significantly less energy maintaining a given speed than a normal runner would. In other words, he would normally be at the back of the pack, but the artificial limbs place him near the front.
This is not unusual, though -
http://www.nytimes.com/2009/05/21/sports/21swim.html
Lots of "technical aids" are banned from competition. Even knee braces for injury and support have to be approved (and proven to not add advantage).
Let him compete all he wants in the paralympics.
Disallow him from competing in the olympics.
In the same way that many athletes believe you have to use drugs in order to compete, if such devices are allowed, eventually every athlete will have to use them to compete.
Imagine if a front-runner got that 30% energy saving boost, rather than the mediocre runner described in the article? I suspect a lot of athletes, who already destroy their bodies with training and drugs, would be more than happy to give up their lower legs if it guaranteed them a few more golds.