It seems unlikely, however, that cannabis use violates the spirit of sport, which the World Anti-Doping Agency defines as “the ethical pursuit of human excellence through the dedicated perfection of each athlete’s natural talents.” Use of a substance that causes little to no harm when used recreationally, infrequently, and safely in an adult’s private life does not, in my opinion, satisfy this criterion. At a minimum, we can argue that cannabis no more meets the Agency’s criteria than another substance that is conspicuously not prohibited: alcohol. There are other arguments against barring athletes who use cannabis. Urine drug testing is a tricky science. Tests can be fraught with false positives — instances in which an individual tests positive but never used the substance, which could happen if, for example, an athlete eats a hemp-containing food product. Tests can also result in false negatives, which occur when an athlete used a substance but the test missed it. Cannabis is also slow to clear from the body. Unlike many other ‘water-soluble’ substances such as stimulants that are eliminated from the body in one to three days, tetrahydrocannbinol is a fat-soluble substance that is eliminated more slowly and typically takes a week to clear from the urine. In individuals who use cannabis more frequently, full elimination can take up a month. In other words, an athlete testing positive for cannabis may not have used for weeks.