Seven-time Tour de France champion and cancer survivor Lance Armstrong has vehemently denied using performance-enhancing drugs his entire career.
The U.S. Anti-Doping Agency disagrees.
On Monday, Armstrong filed a federal lawsuit against the USADA, saying the agency's rules violate athletes' right to a fair trial, as well as claiming the agency does not have jurisdiction in such a case.
After a two-year federal criminal investigation into Armstrong turned up no charges in February, the USADA says it has more evidence to use against the cyclist.
The anti-doping agency says up to 10 former teammates and associates are willing to testify against him and that it has blood samples from 2009-2010 that are "fully consistent" with doping.
Armstrong says he has been tested more than 500 times without once yielding a positive test. He retired from the sport in 2011.
According to ESPN's T.J. Quinn, no athlete has ever filed this type of lawsuit against the USADA successfully.