By: Tapan R. Oza, Esq. and Brant Kuehn, Esq.
Greenspoon Marder’s inaugural blog post about cross-border disputes and all things arbitration begins with a rarity: a U.S. court confirming an arbitration award that gave preclusive effect to a decision by the Lausanne, Switzerland-based Court of Arbitration for Sport (CAS).[1] While that international institution is recognized in the U.S. as the forum for deciding high-profile disputes—like the challenge to Jordan Chiles’ bronze medal at the 2024 Summer Olympics, an award Switzerland’s highest court partially annulled in January 2026—it gets less attention in U.S. courts. However, on Friday, September 18, 2026, a Southern District of New York court upheld a different arbitration award that prohibited the parties from relitigating issues dealt with in a prior CAS award, under New York principles of collateral estoppel.
The underlying dispute concerned a doping charge by the International Tennis Integrity Agency (ITIA), the Women’s Tennis Association (WTA) Tour’s delegated anti-doping authority, against Tara Moore, a British tennis player who resided in the U.S. Ms. Moore was in Bogotá, Colombia, in April 2022, when she tested positive for two substances prohibited by the WTA’s anti-doping rules (boldenone and nandrolone). In October 2019, a male tennis player, Robert Farah, had tested positive for one substance, but an investigation determined his positive test resulted from eating contaminated meat. The ITIA had met with Mr. Farah, and according to Ms. Moore, the WTA Tour had issued a warning to its players about contaminated meat in February 2022 ahead of a tournament in Guadalajara, Mexico. Ms. Moore claimed the WTA Tour should have issued similar warnings in advance of the Bogotá tournament.
There were three proceedings:
- Initially, an independent tribunal found Ms. Moore’s positive tests were, on the balance of probabilities, due to contaminated meat.
- On the ITIA’s appeal, the CAS determined, after an evidentiary hearing and in a split decision, that Ms. Moore could not prove that contaminated meat was the source of the nandrolone in her system. The panel also said it did “not see how this situation could create any obligation on ITIA (or the WTA) to warn the player against eating meat in Colombia prior to the Copa Colsanitas tournament.”
- Moore did not challenge the CAS decision but had already begun an arbitration against the WTA Tour before the American Arbitration Association, on the same day the ITIA appealed, for negligence and breach of the duty of good faith and fair dealing for failing to warn about contaminated meat. When the CAS decided the appeal, the arbitrator gave collateral estoppel effect to the CAS decision, even though the WTA Tour had not been a named party to the CAS proceeding.
Ms. Moore claimed that she was deprived of a fair hearing and that the arbitrator exceeded her powers. Ms. Moore’s first argument claimed that the arbitrator “imported” an “unfair standard” and precluded her from presenting evidence on the duty to warn. The court rejected that argument, agreeing with the WTA Tour that the CAS’s standard requiring Ms. Moore to prove a defense by a “balance of probabilities” was “functionally identical to the preponderance standard” applied in New York state law claims. The court also rejected Ms. Moore’s second argument because New York law applied according to the contract, and the arbitrator applied New York law of collateral estoppel, providing “reasonable, law-consistent bases for its decision.”
This decision is notable because it upholds an arbitration award that treated a prior decision by the CAS, a specialized sports tribunal, as binding on later proceedings. It shows that arbitrators applying New York law may rely on unchallenged decisions issued in foreign jurisdictions to prevent issues from being re-litigated, particularly given the deference courts generally give to arbitration awards. It also confirms that the “balance of probabilities” standard used in some international proceedings is equivalent to the “preponderance of the evidence” standard under New York law. Practically, this decision provides more protection to sports governing bodies than to athletes, who often face the anti-doping rules’ presumption of intentional use; after this decision, a CAS finding made under that presumption can also defeat a later damages claim in the U.S. against a different defendant, even in instances where the organizations may seem to be better equipped with knowledge and authority to warn athletes about possible sources of contamination. Not only had the ITIA asked the World Anti-Doping Agency about meat contamination in January 2022, but also WTA itself had warned about it prior to a different tournament in February 2022, two months before the Bogotá tournament.
Greenspoon Marder’s cross-border disputes team advises clients on international arbitration, multinational commercial disputes, recognition and enforcement proceedings, and complex matters spanning multiple jurisdictions. In collaboration with colleagues across the firm’s corporate, litigation, and international practice areas, we help clients address the legal and business challenges that accompany cross-border disputes. As global commerce becomes increasingly interconnected, we will continue to monitor and analyze noteworthy developments in international arbitration and cross-border dispute resolution, helping clients understand the practical implications of emerging decisions and evolving legal standards.
[1] A search [(cour! OR tribun!) /3 arbitr! /3 (spor! OR deport!)] on Westlaw for decisions referencing the Court of Arbitration for Sport returns only 31 Cases and 1 Trial Court Order.
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