Answer by taking a quote from the following article:

Oscar Leonard Carl Pistorius was born to Henke and Sheila Pistorius on 22 November 1986 in Sandton, Johannesburg, in what was then Transvaal Province (now Gauteng Province) of South Africa. He grew up in a Christian home and has an elder brother, Carl, and a younger sister, Aimee. Pistorius credits his mother, who died at the age of 43 when Pistorius was 15 years old, as a major influence in his life. Pistorius is a white South African with Italian ancestry from his maternal great-grandfather, who was an Italian emigrant to Kenya.

Pistorius has been the subject of criticism because of claims that his artificial limbs give him an advantage over runners with natural ankles and feet. He runs with J-shaped carbon-fibre prosthetics called the "Flex-Foot Cheetah" developed by biomedical engineer Van Phillips and manufactured by Ossur.  On 26 March 2007, the IAAF amended its competition rules to include a ban on the use of "any technical device that incorporates springs, wheels or any other element that provides a user with an advantage over another athlete not using such a device". The IAAF stated that the amendment was not specifically aimed at Pistorius. To decide whether he was running with an unfair advantage, the IAAF monitored his track performances using high-definition cameras to film his race against Italian club runners in Rome on 13 July, and his 400 metres in Sheffield on 15 July 2007, at which he placed last.  In November 2007, Pistorius was invited to take part in a series of scientific tests at the Cologne Sports University under the guidance of Professor of Biomechanics Dr Peter Bruggemann in conjunction with Elio Locatelli, who was responsible with the IAAF of all technical issues. After two days of tests, Bruggemann reported on his findings on behalf of the IAAF. The report claimed that Pistorius's limbs used 25% less energy than runners with complete natural legs to run at the same speed, and that they led to less vertical motion combined with 30% less mechanical work for lifting the body. In December, Bruggemann told Die Welt newspaper that Pistorius "has considerable advantages over athletes without prosthetic limbs who were tested by us. It was more than just a few percentage points. I did not expect it to be so clear." Based on these findings, on 14 January 2008, the IAAF ruled Pistorius's prostheses ineligible for use in competitions conducted under the IAAF rules, including the 2008 Summer Olympics. Pistorius called the decision "premature and highly subjective" and pledged to continue fighting for his dream. His manager Peet van Zyl said his appeal would be based on advice from United States experts who had said that the report "did not take enough variables into consideration".  Pistorius subsequently appealed against the adverse decision to the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland, and appeared before the tribunal at the end of April 2008. After a two-day hearing, on 16 May 2008, the Court of Arbitration for Sport upheld Pistorius's appeal and the IAAF council decision was revoked with immediate effect. The CAS panel unanimously determined that Dr Bruggemann tested Pistorius's biomechanics only at full-speed when he was running in a straight line (unlike a real 400-metre race); that the report did not consider the disadvantages that Pistorius suffers at the start and acceleration phases of the race; and that overall there was no evidence that he had any net advantage over non-disabled athletes. In response to the announcement, Pistorius said: "My focus throughout this appeal has been to ensure that disabled athletes be given the chance to compete and compete fairly with non-disabled athletes. I look forward to continuing my quest to qualify for the Olympics."

What caused the dispute?
He runs with J-shaped carbon-fibre prosthetics called the "Flex-Foot Cheetah"