(CNN) -- Lance Armstrong is fighting to not only keep his seven Tour de France titles, but also maintain his reputation as one of sport's most remarkable athletes.
The American lost his latest legal bid to halt the U.S. Anti-Doping Agency's case against him, which has come more than a year after his retirement from cycling and subsequent move to triathlon competitions.
The 40-year-old, who fought back from testicular cancer to win cycling's biggest race from 1999 to 2005, has described himself as the "most tested athlete in the world" and long denied any involvement with illegal doping.
"Lance has passed nearly 500 tests over 20 years of competition," declared spokesman Mark Fabiani in response to allegations from disgraced former teammate Tyler Hamilton -- who has admitted taking performance-enhancing drugs during his career.
However, the former chairman of the World Anti-Doping Agency, Dick Pound, has long argued that Armstrong was involved in the dark art of doping.
"Look all around him and everyone else is doing it, so what should you think?" Pound told the New York Times.
After months of legal arguments, the two parties are now left with no option other than solving the dispute between themselves. So where did the charges come from, and how did the two sides develop such a bitter relationship?
What are the charges?
In June 2012, the USADA charged Armstrong with doping and trafficking of performance enhancing drugs.
Along with the cyclist, several members of Armstrong's former team were charged. These included Luis Garcia del Moral and Michele Ferrari, both team doctors, trainer Jose "Pepe" Marti, team physician Pedro Celaya and Johan Bruyneel, director of the U.S. Postal Service (USPS) team.
"Armstrong is facing some pretty serious charges from USADA," explains Peter Flax, editor of Bicycling Magazine.
"He's been accused of the use of of prohibited performance-enhancing drugs and methods, as well as being involved in the possession, trafficking, and concealment of these activities. The list of drugs and doping methods is pretty much the kitchen sink of what was possible in the era in which Armstrong rode."
It is believed the charges stem from a federal investigation by Food and Drug Administration special agent Jeff Novitzky. His investigation didn't result in any charges, but Novitzky -- who led the fight against the Balco Laboratory and doping in Major League Baseball -- is understood to have helped with the USADA case.
What is the USADA?
The U.S. Anti-Doping Agency is the body responsible for monitoring in and out of competition drug testing for U.S. Olympic and Paralympic sports.
It is responsible for enforcing the World Anti-Doping Agency code, and its bans apply around the world.
"USADA's job is to protect clean sport rather than enforce specific criminal laws," its chief Travis T. Tygart said at the time of the federal case's collapse.
"Our investigation into doping in the sport of cycling is continuing and we look forward to obtaining the information developed during the federal investigation."
What is the evidence?
The USADA alleges that Armstrong took steroids throughout his career, and says it has testimony from former teammates to support the charges. The organization has refused to reveal who has provided the evidence.
"A significant number of Armstrong's former teammates, in return for immunity or preferential treatment from USADA, have testified about doping activities that they participated in or witnessed," Flax told CNN.
"Some of them, like Floyd Landis, are people who have made public accusations in the past, but others -- most notably George Hincapie, Armstrong's most loyal lieutenant during all seven of his Tour de France victories -- have never offered testimony about doping on that team."
Landis, a rider with the USPS team from 2002 to 2004, has publicly claimed that he saw Armstrong using blood transfusions to increase the level of oxygen-carrying red blood cells in his system, as well as taking the blood-boosting drug EPO.
In 2006, Landis became the first person other than Armstrong to win the Tour since the late Marco Pantani in 1998 -- the Italian being another rider whose career was marred by doping allegations -- but was stripped of the title for failing a drugs test. The disgraced cyclist has even gone as far as accusing Armstrong and Bruyneel of paying the International Cycling Union (UCI) to cover up a positive test in 2002.
Armstrong dismissed the charges, and accused his former colleague of threatening riders with drug allegations.
"While these types of repeated, tired and baseless accusations against Lance have been proven false in the past, it is quite regrettable, but telling that so many in cycling are now attacked by a bitter and scorned Landis who, quite simply, has zero credibility," declared a statement released on Armstrong's behalf.
After years of accusations, the USADA's case is the biggest threat to Armstrong's record yet.
"I think the amount of info they have to make a claim that they have proof that Lance doped is pretty significant and I think that is why there is such interest in this. It's a mess, but I think they may finally have the goods on Lance," Flax said.
Who has been found guilty so far?
Former team doctors Del Moral and Ferrari have been handed lifetime bans for their part in the doping case, as has the team's former trainer Marti.
Ferrari, who was a consultant during Armstrong's seven-year reign, was accused of developing a mixture of testosterone and olive oil that could be taken orally, and helped aid recovery. Ferrari apparently also helped riders inject EPO to help avoid detection in urine samples.
Del Moral was accused of helping the riders with blood transfusions, and saline infusions to prevent detection. He was also accused of administering a range of banned drugs to members of the team.
Marti was given a lifetime ban for delivering a variety of banned products to the team from his base in Valencia, Spain.
What is Armstrong's defense?
The main thrust of Armstrong's defense is that he is the victim of a witch hunt by the USADA.
"Though USADA claims it has collected at least 10 witnesses to these events, it refuses to name a single one or even to identify what they will say," argues Armstrong's legal team, in a response to the charges published on the cyclist's website.
"USADA also claims that Mr. Armstrong committed doping violations for years, but cannot produce a single positive test result to corroborate this claim.
"Curiously, in the face of an alleged conspiracy involving four separate teams of cyclists over two decades, USADA has decided to charge only a single rider: Lance Armstrong."
Armstrong has also made his feelings clear about the USADA's offers of immunity to his his former colleagues.
"So let me get this straight... come in and tell them exactly what they wanted to hear and you get complete immunity AND anonymity? I never got that offer. This isn't about Tygart wanting to clean up cycling; rather it's just a plain ol' selective prosecution that reeks of vendetta," Armstrong declared on his Twitter account.
The case is still focused on whether the USADA has the right to prosecute Armstrong.
"The legal arguments center upon the jurisdiction of the U.S. Anti Doping Agency. In essence Lance Armstrong is trying to adopt a legal argument that the agency should not be prosecuting the regulatory and disciplinary process. Armstrong is saying the agency is violating his human rights," sports lawyer Richard Cramer told CNN.
"However the Federal Judge has rejected Armstrong's application and at the moment the agency will be allowed to proceed, although there is the added complication on whether it should be the International Cycling Union which should be prosecuting the charges."
What legal stages has the case been through, so far?
June 2012 : USADA officially charges Armstrong with doping and trafficking
July 9, 2012: Armstrong files a lawsuit against the USADA in Austin, Texas. A judge throws it out on the same day.
In his order dismissing the suit, Judge Sam Sparks was highly critical of the case brought by Armstrong and his legal team.
"Armstrong's complaint is far from short, spanning 80 pages and containing 261 numbered paragraphs, many of which have multiple sub parts," he said.
"Worse, the bulk of these paragraphs contain 'allegations' that are wholly irrelevant to Armstrong's claims and which, the Court must presume, were included solely to increase media coverage of this case, and to incite public opinion against Defendants.
"Indeed, vast swaths of the complaint could be removed entirely, and most of the remaining paragraphs substantially reduced, without the loss of any legally relevant information."
July 10, 2012: Armstrong files a new lawsuit against the USADA. The suit asks the judge to prevent the agency from removing him of his seven Tour de France titles and banning him for life if he fails to enter arbitration with them.
Ferrari, del Moral and Marti are handed lifetime bans by USADA
August 20, 2012: Judge Sparks dismisses Armstrong's case against USADA. Sparks says the court "cannot interfere" in the case.
"The Court finds they are best resolved through the well-established system of international arbitration, by those with expertise in the field, rather than by the unilateral edict of a single nation's courts," said Sparks, before admitting there may be a basis for some of Armstrong's concerns.
"USADA's conduct raises serious questions about whether its real interest in charging Armstrong is to combat doping, or if it is acting according to less noble motives."
Despite Armstrong supposedly facing a three-day deadline to agree to arbitration with the agency, many believe the case still has a long way to go before a final result is seen.
"This is only the start of what is likely to be a hotly contested and disputed regulatory disciplinary process. Armstrong and his legal team will take every point to ensure there is a not guilty finding," Cramer, of UK-based FrontRow Legal, told CNN.
"I would expect the process to last several months and possibly years. Armstrong has an awful lot to lose and he clearly has the strength and willpower to fight his corner."
What are the sanctions is Armstrong facing?
If found guilty, Armstrong would face a lifetime ban from all sports covered by the World Anti-Doping Agency. Along with cycling, this would prevent Armstrong from competing in triathlon -- in which he is currently suspended pending the outcome of these charges.
Armstrong would almost certainly be stripped of all his Tour de France titles.
"Deals have been made with other former champions who committed the same offenses. So the jerseys, if they are taken away from Lance Armstrong, will be given to other people who have been convicted of doping," Flax said.
"Justice is just not on the table anymore, this is really something which is a giant mess."
What does the International Cycling Union say about the issue?
The UCI claims that it has the authority to investigate and possibly sanction Armstrong. Both bodies are recognized by the International Olympic Committee, but disagree over which should pursue the Armstrong case.
Ultimately, the USADA has the authority to sanction Armstrong, so there is little the UCI (or the cyclist) can do to stop the current case.