Mike Tyson, Jake Plummer, Ricky Williams and Floyd Landis are among more than 150 current and former athletes who support a petition to remove marijuana from the World Anti-Doping Agency’s prohibited substances list.

Athletes for CARE requested WADA – the organization that sets drug policy for Olympic sports – remove THC from its banned list in a letter Thursday. Athletes for CARE, a non-profit that advocates for research into cannabis as a treatment for brain injury and other health issues, also announced a petition on Change.org.

“We have found an improved quality of life through cannabis and natural cannabinoids, including significant therapeutic and wellness benefits, and these positives should be freely available to all other athletes,” read the letter to the WADA group of experts that is developing the 2021 banned list.

“In keeping with WADA's values of ethics, fair play and honesty, the organization owes it to athletes to allow full access to this gentle but effective plant medicine."

As states and municipalities have legalized marijuana for medical and recreational use in recent years, sports leagues and organizations have been slow to change their stances on the drug.

"It is important to note that the list is not static but evolves based on new scientific evidence, as well as, to a lesser degree, changes of use and cultural elements," WADA spokesperson James Fitzgerald said in an email to USA TODAY Sports. "Therefore, WADA maintains dialogue with athletes, administrators, scientific experts and other stakeholders and closely follows the literature in this area to obtain new evidence and information as it becomes available."

For a drug to be banned, WADA officials must find that a substance meets two of the three following criteria: it has the potential to enhance sport performance, it represents a health risk to the athletes and/or it violates the spirit of sport.

"While the change in legal status of cannabis in some areas of the world may be one of many factors addressed during deliberations, legal status is not one of the three criteria to be fulfilled for inclusion of a substance in the list," Fitzgerald said.

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WADA raised the threshold for THC – the chemical in marijuana that creates a “high” – in 2013. At the same time, WADA took marijuana off the slate of drugs tested out of competition.

Still, there were 154 positive tests for THC in 2017, the most recent annual testing figures released by WADA. Soccer (12) and basketball (10) were the only sports that had double-digit positive tests for marijuana in 2017.

Eleven U.S. athletes tested positive for marijuana and were given six-month bans – although half the bans was deferred in each case – since 2013: Spencer Walden (track and field), Lauren Mulwitz (cycling), James Howe (taekwondo), Angelique Matsushima (weightlifting), Riley Stohr (luge), Jay Henderson (cycling), Anthony Ferraro (Paralympic judo), Stephen Bedford (cycling), Cory Juneau Scott (skateboarding), Cheyenne Schenk (weightlifting) and Devin Logan (skiing).

Kelvin Gastelum and Nate Diaz – two of the top MMA fighters in the world – also tested positive since the U.S. Anti-Doping Agency was brought on to test UFC fighters in 2015. Each got the same ban, which is the equivalent of a three-month suspension.

Cannabidiol (CBD) – typically found in oil form in health food stores – is not banned by WADA. CBD, which has been marketed to treat a myriad of ailments, does not contain THC.

“Athletes for CARE is proud to have such a strong network of respected athletes campaigning for the removal of cannabis from the World Anti-doping Agency’s prohibited substance list,” Anna Symonds, a rugby player and Athletes for CARE representative, said in a statement. “We’re also calling on fans to show their support online via our Change.org petition.”

Follow A.J. Perez on Twitter @byajperez