However, Diaz, 31, may yet be punished by the United States Anti-Doping Agency (Usada), who are still investigating the case.
The Stockton-born fighter smoked the substance, known as CBD, through a vape pen during his post-fight press conference after losing a tight five-round contest to McGregor.
When asked why he was smoking CBD, he said: “It helps with healing process, inflammation, stuff like that. So you want to get these before or after the fight, it’ll make your life a better place.”
CBD is a key ingredient in cannabis but – unlike THC, the drug’s other main compound – it is non-psychoactive. This makes it useful for medicinal purposes.
Cannabinoids – the chemical compounds contained within cannabis – are nevertheless listed as prohibited in-competition substances by the World Anti-Doping Agency.
According to the UFC’s anti-doping policy, an ‘in-competition’ period is defined as the six hours prior to the commencement of the scheduled weigh-in and, crucially, the six hours after the conclusion of the fight.
The company’s anti-doping policy was written in conjunction with Usada, who therefore could still punish Diaz if they judge his vaping to be an anti-doping violation.
Diaz’s elder brother, Nick, was banned for five years by Usada after testing positive for cannabis, only for his suspension to be reduced to 18 months.
The elder Diaz’s drug suspension expired at the start of last month.
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