Valdez was criticized this week when it emerged that he tested positive for the banned substance phentermine, best known as an appetite suppressant. The substance is banned by the Voluntary Anti-Doping Association (VADA) but is not considered banned by the World Anti-Doping Agency (WADA) when used "off competitions".
Valdez tested positive for the substance in a test conducted on August 13. He tested negative in a test conducted on August 30.
After reviewing the situation, the Pascua Yaqui Tribal Athletic Commission, under whose auspices this evening of boxing will be held in Arizona, and the World Boxing Council (WBC) gave the go-ahead for the bout.
"I have never used banned substances to improve my performance. I have never used them and I will not do so. I have respected anti-doping tests since my amateur days and now as a professional," Valdez said.
"And since I've turned professional, I've gone through over 30 anti-doping programs, which we always ask ourselves, and we make sure that [doping testing] is included in the contract to take VADA tests to keep our sport clean and make sure that no one gets an unfair advantage."
WBC President Mauricio Sulaiman explained his organization's decision to allow Valdez to conduct a title defense.
"We formed a panel of experts, we had meetings for three days. We had meetings and an audience with Valdez and his team, with the boxing commission, which is the sanctioning commission where the fight takes place. The substance found does not offer any competitive advantage in the fight. The advantage of the substance is the equivalent of three energy drinks," Sulaiman said.
"During our investigation, we found no wrongdoing on the part of Valdez, no intent, no situation from which he could have improperly benefited. This substance does not give him any advantage. Therefore, we have decided to allow him to fight for the world title", Sulaiman said.