The Court of Arbitration for Sport has for decades served as the final arbiter on sports disputes throughout the world, ruling on thousands of cases ranging from trifling to momentous. The court enabled Oscar Pistorius to run against able-bodied athletes, upheld the cyclist Floyd Landis’s doping suspension and prevented Luis Suárez from overturning his suspension from soccer for biting an opponent at the 2014 World Cup.

All Olympic federations and the World-Anti Doping Agency recognize the court’s supremacy, and athletes can compete only if they waive their right to bring sports cases to their national courts by signing arbitration clauses binding them to the sports court, which is based in Lausanne, Switzerland.

A speedskater from Germany, however, is on the verge of turning this entrenched system of justice on its head. Claudia Pechstein, Germany’s most decorated Winter Olympian, has challenged the fairness of the Court of Arbitration for Sport in a German court, and a ruling next month could drastically alter how justice is meted out in the sports arena. If she prevails, athletes may be able to bypass international sports’ normal dispute-resolution systems and instead seek redress for their grievances through their national courts — a radical notion considering the vastly different justice systems around the world.

“If we are successful, all athletes might think about circumventing the CAS,” said Thomas Summerer, one of Pechstein’s lawyers.

Pechstein, 43, was barred from competition for two years by the international governing body for speedskating in 2009 after antidoping authorities testing samples of her blood found what they believed were abnormal levels of reticulocytes, or immature red blood cells, often an indicator of doping. Pechstein emphatically denies doping and says the irregularity is the result of a congenital blood disorder.

“I don’t wish what happened to me on anyone,” she said in a phone interview from Berlin. “It’s hell.”

Next month, Germany’s Federal Court of Justice, the country’s highest civil court, will decide whether to uphold a ruling issued last January by the Munich Higher Regional Court, which went against both the Court of Arbitration for Sport and the Swiss Federal Tribunal, allowing Pechstein to proceed with a lawsuit seeking 4.4 million euros, almost $5 million, in compensation from her sport’s governing body, the International Skating Union, for lost income.

Mike Morgan, the founding partner of Morgan Sports Law, who has represented athletes and national Olympic committees before the sports court, said that a ruling in Pechstein’s favor would “definitely send shock waves through sports arbitration.”

“This will have an impact like the Bosman ruling,” said Richard Ings, a former head of the Australian Anti-Doping Agency, referring to the 1995 European Court of Justice decision that transformed how soccer players could move among teams.

Created in 1984 by Juan Antonio Samaranch, then the president of the International Olympic Committee, the Court of Arbitration for Sport filled a need for a specialized international arbitration tribunal able to resolve sporting disputes expeditiously and without political influence.

With the I.O.C. controlling and financing the court, concerns about its impartiality escalated. After a ruling from the Swiss Federal Tribunal raised questions about these cozy links in 1994, the International Council of Arbitration for Sport was created to manage the court, independent of the I.O.C.

The court’s annual budget has more than doubled, to $13.9 million in 2015 from $5.6 million in 2005. Its 356 arbitrators from 81 countries received a record 503 filings in 2015, compared with 232 during the 1990s.

National courts have largely deferred to the sports court’s decisions. But that changed when the Munich court issued its ruling, declaring both a sports court decision upholding the International Skating Union’s ban and Pechstein’s signed arbitration clause invalid.

The court determined that since the skating organization controls the market for speedskating events, its use of arbitration clauses binding athletes to the sports court constituted an abuse of a dominant position under German antitrust law. The German court said it found a structural imbalance within the sports court that favored sports governing bodies over athletes.

The imbalance, according to the court, involves the composition of the International Council of Arbitration for Sport, which administers the sports court and whose 20 members are nominated primarily by the I.O.C. and international sporting organizations. John Coates, an I.O.C. vice president, is president of the international council, which has a critical influence because it appoints the sports court’s arbitrators. And in each three-member arbitration panel — after both parties to a dispute have selected an arbitrator — an international council member selects the president of the panel. This creates a risk, according to the Munich court, that each panel could be skewed against athletes.

Though initially optimistic before her case was heard by the sports court, Pechstein said she was left disillusioned. “What do you expect from a court whose judges are mostly appointed by the sports’ governing bodies?” she said. “Athletes don’t have a chance at a fair trial.”

Pechstein said that she lost sponsors and that her reputation was damaged as a result of the more than six-year legal battle. She described the Munich court’s ruling as a “success worth more than all of my Olympic medals.” (She has won nine over all, including five golds.)

FIFPro, the global soccer union, announced its support of Pechstein in July. “The independence and impartiality of the CAS is an issue that concerns a large number of athletes,” said Jonas Baer-Hoffmann, a FIFPro policy director.

The Pechstein decision “put everything on its head,” said Paul Greene, the founder of the sports law firm Global Sports Advocates L.L.C. “Anyone who goes outside the CAS system generally loses.”

Consider the American sprinter Justin Gatlin. In 2008, a Florida court characterized his four-year doping ban — which was upheld by the sports court — as “arbitrary and capricious,” and in violation of the Americans With Disabilities Act. But it ultimately concluded that he was bound to the sports court, a decision the judge admitted was “quite troubling” because it meant “United States courts have no power to right the wrong perpetrated upon one of its citizens.”

Pechstein said her case was “a real awakening for many athletes.”

Robert Harting, a German who won gold in the discus at the 2012 London Olympics, has been one of Pechstein’s staunchest supporters. Many athletes, he said, believe mandatory arbitration is unfair but sign anyway so they can compete, and clean athletes who believe they have been wrongfully barred by the sports court have no other option to clear their name.

“Why should I sign an arbitration agreement, which takes away all my rights and doesn’t give me the chance to fight against a wrong judgment?” Harting said in an email.

(Appeals to sports court rulings can be made to the Swiss Federal Tribunal, but the group vacates sports court awards based on public policy violations or procedural missteps, and not on merit.)

The sports court issued a statement after the Munich court’s ruling, contending that if other countries followed suit, then “the basic principles of international arbitration would be compromised.”

Since then, the sports court has announced some reforms. It said in December that it would grant athletes’ commissions the opportunity to send nominations for arbitrators to the International Council of Arbitration for Sport. But Morgan and Summerer say athletes’ commissions — composed of former and current athletes often appointed directly by the I.O.C. and WADA — lack the independence to represent athletes in the way a players’ union would.

The sports court has many defenders, many of whom say legal chaos would ensue if athletes could turn to their own countries’ justice system to challenge sanctions.

Looking at arbitration clauses “as a gun to your head is ignoring the alternative,” said Andrew de Lotbinière McDougall, a sports court arbitrator and partner at White & Case in Paris. He added, “You can imagine the lack of consistency in decisions about matters such as doping and team selection between national courts in different countries.”

Matthieu Reeb, the secretary general of the sports court, noted that the group has introduced improvements, including legal aid for those who might struggle to pay arbitration costs.

“It’s in the interest of athletes to use the services of the CAS rather than going before the civil courts with procedures and appeals that can last for several years,” he said. “The CAS is quicker, more efficient and adapted to sport.”

Pechstein’s lengthy court battle seems to support Reeb’s belief. But, she said, “Justice is what matters, not speed.”

“Generally, you can have a pretty fair shake at the CAS,” Morgan said. “Rather than disband it and start all over again, it needs to listen to the athlete groups and learn from the Pechstein case.”

Pechstein said she was eager to close this legal process so she could focus on qualifying for the 2018 Winter Games, where she hopes to be Germany’s flag-bearer days before her 46th birthday.

“It would be the perfect ending for my rehabilitation,” she said.