Australian swimmer Shayna Jack has always denied consuming ligandrol, a banned performance enhancing drug. But, when Jack was subject to an out-of-competition anti-doping test at Tobruk Pool in Cairns in 2019, she returned an adverse analytical finding. As is protocol, Jack was issued a provisional suspension, the suspension was made public and the swimmer was ultimately handed a four-year ban from the sport.

On appeal, Jack insisted that she had not knowingly taken ligandrol. She speculated that legal supplements she was taking might have been contaminated, or that she could have come into contact with the substance while using public pool facilities. But because the global anti-doping regime operates on a strict liability basis, a lack of evidence that Jack did not knowingly ingest ligandrol was insufficient.

Related: Wada defends its actions over Chinese swimmers’ doping allegations

In the Court of Arbitration for Sport, the arbitrator described being “greatly impressed” by Jack’s witness evidence. The swimmer presented as someone “who conscientiously sought, at all times, to comply with the anti-doping policies of [Swimming Australia]”. Yet, despite the arbitrator accepting that Jack had not intentionally taken performance enhancing drugs, despite a legion of character witnesses describing the swimmer as “hardworking, conscientious, likeable and motivated athlete of the highest integrity,” all the arbitrator could do was reduce the suspension from four years to two. All this played out in a very public manner.

With its strict liability, utmost transparency and onerous burdens of proof, the global anti-doping system overseen by the World Anti-Doping Agency can result in cases of individual injustice. Jack is exhibit A – banned for two years at the prime of her career even though an arbitrator accepted the ligandrol in her system was ingested accidentally, and with no performance enhancing intent. Peter Bol is exhibit B – publicly suspended for testing positive to synthetic erythropoietin, only for the case to be withdrawn due to seemingly botched testing.

While the Bol case has led to some important changes, the bedrock of the anti-doping system remains. Athletes are responsible for what ends up in their body, however it gets there, subject to narrowly-defined exceptions that are considered under close, transparent scrutiny. In the arms race of performance enhancement, where anti-doping authorities are perennially playing catch-up, this is the settlement we have collectively reached – unfairness in some cases in the interest of confidence in the system as a whole. In some ways it is the opposite of Blackstone’s famous ratio on criminal justice – that it is better 10 guilty people go unpunished than one innocent suffers.

But this only works in sport if everyone is subject to the same rules. And news that 23 Chinese swimmers tested positive for a prohibited substance, trimetazidine, only to compete and in some cases win medals months later at the Tokyo Olympics, has shaken the swimming world to its core.

With less than 100 days to go until the Paris Games, athletes, national federations and anti-doping authorities around the world have been left shocked and angry. The furore suggests an acrimonious pool meet in Paris, reminiscent of the feud between Australian Mack Horton and China’s Sun Yang (whose four year anti-doping suspension ends next month), but on a far grander scale.

Australia’s swimmers are not hiding their feelings. Emma McKeon, who won four gold medals in Tokyo, shared a quote from Horton on her Instagram account. “This news is infuriating,” it said. “I feel for the deserving athletes who have missed out on life-changing medal opportunities due to a failed system.” McKeon won bronze in the 100m butterfly in Tokyo, behind China’s Zhang Yufei – one of the athletes to test positive.

Backstroke star Kaylee McKeown, who won three gold medals in Tokyo, shared the same quote – McKeown and McKeon were both part of Australia’s 4x100m medley relay team which finished third behind China. So did freestyle queen Ariarne Titmus – together with McKeon, part of the 4 x 200m freestyle relay squad that placed third in a race won by a world record-breaking Chinese effort.

Confusion swirls over these revelations. The environmental contamination theory put forward by the Chinese athletes and accepted by Wada is not entirely implausible – all 23 positive tests occurred at the same time and place, and in too small a quantity to likely be performance enhancing. That hardly sounds like wholesale state-sponsored doping. But question marks remain – how does a drug, used as heart medication, only found in tablet form, end up contaminating a kitchen? And why was this never made public until an investigation by the New York Times and German broadcaster ARD?

On Twitter, former long-time head of Australia’s anti-doping authority, Richard Ings, has defended Wada’s handling of the case, pointing to specific rules around environmental contamination, Wada’s receipt of external legal advice and the difficulties posed by the pandemic, which hampered an investigation. But that is not the view of everyone. A seasoned sports lawyer told the Guardian that the saga demonstrates “Wada is not fit for purpose to be regulator, investigator, and adjudicator”.

Related: Peter Bol case prompts Wada to reform synthetic EPO testing processes

The story certainly leaves the global anti-doping authority with important questions to answer – questions not brushed aside by threatening critics, including the head of the United States Anti-Doping Agency, with legal action. China’s long history of anti-doping issues, particularly in the pool, only compound concerns. The anti-doping regime is premised on retaining public trust and confidence in athletic performance; Wada’s opacity at the time and adversarial reaction now undermine this. As British swimming great Adam Peaty asked, “why not release this information at the time, who really benefits from the lack of transparency and secrecy?”

All of which promises a combustible atmosphere when the world’s swimmers converge in Paris in three months’ time. Likely joining them there will be Shayna Jack, now returned to the pool after her doping ban, and an important member of Australia’s relay teams. While her colleagues have spoken out, Jack has remained silent on the current controversy. But she would be forgiven for wondering why she was treated so differently.