Lance Armstrong responded to recent doping allegations against him by accusing the U.S. Anti-Doping Agency (USADA) of violating its own regulations and even possibly breaking federal law through its investigation.

The agency accused the champion cyclist of using performance-enhancing drugs in order to win cycling events such as the Tour de France, which he dominated from 1999 to 2005. Friday was the last day Armstrong could reply to the USADA's allegations before his case moved forward.

If the investigation finds that the accusations are in fact true, Armstrong could have his titles taken from him and could be completely barred for cycling, despite his retirement from the sport last year.

Armstrong's attorney said in the lengthy document, that the supposed evidence against Armstrong has still been kept secret from him and his client. He further said that they believe that the USADA forced witnesses to present false testimonies against the athlete.

Armstrong's refuting letter said the USADA's case is "long on stale allegations disproved long ago and short on evidence" and "offensive to any notions of due process."

Armstrong encouraged that the case not be reviewed by the review board, which is responsible for deciding whether the evidence presented supports the allegations. Armstrong also questioned the 2009-2010 blood tests taken by the USADA and posted his test results on his website, Livestrong.com, which showed negative results for drugs.

The letter also added that the allegations against him are not within the USADA's eight-year statute of limitations. However, the agency has rebutted this saying that Armstrong continues to prolong the time limit through his denial of drug use.