Two-time grand slam champion Simona Halep has been cleared for an immediate return to tennis after sport’s highest court accepted she was not entirely at fault for her positive doping test at the 2022 US Open.

On court, the former top-ranked Halep beat Serena Williams in the Wimbledon final of 2019, one year after winning the French Open.

In court, Halep now has a legal victory that ends a four-year ban in a case that threatened to be just as career-defining had the verdict gone against her.

Instead, the Court of Arbitration for Sport on Tuesday lifted the allegation of suspected doping cheat from the 32-year-old Romanian, whose career has been on hold for more than a year.

Three CAS judges ruled Halep had “on the balance of probabilities” showed her positive test for a banned blood-boosting substance was unintentional and caused by a contaminated supplement.

Halep’s four-year ban was cut to just nine months and, applied retroactively, expired last July.

“I cannot wait to return to the tour,” Halep said in a statement released by her lawyer, Howard Jacobs, who noted she now has a lawsuit against the supplement maker.

She hailed her win against “scandalous accusations” aimed at her and what she called the “seemingly unlimited resources” of tennis authorities who prosecuted her.

The International Tennis Integrity Agency which banned her last year asked CAS to impose an even longer and likely career-ending sanction of up to six years.

Agency chief executive Karen Moorhouse said in a statement they respected the CAS result and the right of athletes to appeal in anti-doping cases.

The CAS judges also awarded Halep 20,000 Swiss francs ($A35,000) towards her legal fees from the ITIA.

Halep has not played since the 2022 US Open, where she tested positive for the banned blood-booster roxadustat. It can help produce more of the natural hormone erythropoietin, or EPO, which has long been a doping product favoured by endurance athletes.

She was provisionally suspended from playing during an investigation that was prolonged by detecting alleged irregularities in her biological passport, which can reveal abnormal blood values measured over several years.

The ITIA banned Halep last September until October 2026 after she would have turned 35.

She denied wrongdoing for the positive test and blamed contaminated nutritional supplements. Athletes need to prove the source of contamination to show they were not at fault for doping.

Halep appealed to CAS and came to Lausanne, Switzerland, one month ago for a three-day, closed-door hearing.

The court said its judges, who dismissed the charge against Halep relating to her blood values, issued the verdict “as soon as practicable” without waiting to deliver a lengthy document detailing all their reasons.

“Although the CAS panel found that Ms. Halep did bear some level of fault or negligence for her violations, as she did not exercise sufficient care when using the Keto MCT supplement, it concluded that she bore no significant fault or negligence,” the court said.

The case was heard by three of the court’s most highly regarded judges. The chair of the panel, Annabelle Bennett of Australia, also oversaw the case brought by two-time Olympic champion runner Caster Semenya that later went to the European Court of Human Rights.

Halep can now resume a career that stalled and left the former No. 1 ranked No. 1138 when the 2023 US Open started.