The Court of Arbitration for Sport was again in the spotlight on Thursday as it halved Russia's punishment for state-sponsored doping, a ruling that still menat the country is banned from a Summer and Winter Olympics.
The 'supreme court of sport' was created in 1984 to deal with the rising tide of legal disputes in the booming business of global sport.
Here AFP looks at its history, organisation and some of the controversial cases it has handled.
What is CAS?
Set up at the urging of then International Olympic Committee President Juan Antonio Samaranch, it became independent in the 1990s.
The court is based in Lausanne. Its arbitrators are appointed on four-year terms that can be renewed. The CAS web site says that in 2007 there were 275 arbitrators without giving a more recent number.
CAS decisions are binding on those involved in sport, although they have the right of appeal to the Swiss civil courts.
In addition to doping cases, the court handles disputes over disciplinary matters and money.
The Russian scandal
The long-running Russian case is unusual in that athletes were suspended as a group, not because they tested positive but because they represented a country found to have organised and institutionalised systematic doping.
In 2016, after the governing body of world athletics, known as the IAAF at the time but since rebranded World Athletics, suspended all Russians from the Rio Olympics except US-based long jumper Darya Klishina, CAS rejected an appeal by 136 Russian athletes for exemptions.
In 2018, after the IOC decided to exclude all Russian sports from the Pyeongchang Winter Games, CAS overturned the bans on 15 Russians saying the evidence was "insufficient".
"An extremely disappointing and surprising decision," said IOC President Thomas Bach.
Russians who did compete did so, as in Rio, under a neutral flag.
On Thursday, CAS gave its latest ruling in the Russian scandal and although it halved a four-year ban that still meant Russia will be banned from the Tokyo Olympics next summer and the Beijing Winter Games the following year.
The doping caseload
CAS has recently handed down high-profile decisions in disputes between Manchester City and UEFA on Financial Fair Play, on the seemingly endless dispute over a payment to Michel Platini when Sepp Blatter was head of FIFA and on Boca Juniors' attempt to have River Plate disqualified in the 2018 Copa Libertadores final.
Yet the Russian decision is the latest in a long series of rulings on drugs.
- Semenya -
In 2019, CAS validated IAAF rules on that impose a maximum testosterone level in women's middle-distance events. This effectively forced Caster Semenya to undergo hormone treatment to run her Olympic distance of 800m distance. The South African and her supporters said this was "discrimination" and appealed.
- Sharapova -
After Russian tennis star Maria Sharapova tested positive for meldonium in January 2016, the month it was added to the banned list, CAS cut her ban from two years to 15 months saying it accepted she did not intend to take banned drugs.
- Sun Yang -
On the other hand, CAS handed triple-Olympic champion Sun Yang a spectacular eight-year ban after the Chinese swimmer smashed a sample he had given during an unannounced doping test in September 2018. A peculiarity of this case is that Yang insisted the hearing was public.
- Cycling -
In 2010, CAS stripped Floyd Landis of his 2006 Tour de France victory after a positive test for testosterone. The American had confessed that he had been doped.
In 2012, CAS upheld a decision by WADA to ban Spaniard Alberto Contador for two years, stripping him of his wins in the 2010 Tour de France and the 2011 Giro after an intricate case in which the cyclist said he had eaten contaminated meat.
Not everyone turns immediately to CAS. Lance Armstrong didn't appeal the decision by the UCI, which runs world cycling, to strip him of his seven Tour de France titles.