Athletes for Care, a nonprofit that lists more than 100 athletes as members, released an open letter Wednesday asking the World Anti-Doping Agency to remove marijuana from its banned list.
Mike Tyson, Floyd Landis, Jim McMahon and Frank Shamrock are listed among the football, basketball and hockey players, along with other athletes, as members of the organization.
"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," the letter reads.
The letter says that cannabis and THC do not meet WADA requirements -- potential to enhance performance, presenting a health risk and violating the spirit of the sport -- for a banned substance. The group also highlights the therapeutic effects of marijuana.
Along with the letter, Athletes for Care has started an open petition to express support for the effort.