The UFC has suspended recently retired light heavyweight Stephan Bonnar for one year, promotion vice president of regulatory affairs Marc Ratner told ESPN.com on Tuesday.
The suspension comes less than a week after Bonnar and heavyweight Dave Herman failed their UFC 153 postfight drug tests.
Bonnar, 35, tested positive for Drostanolone, an anabolic steroid. Herman tested positive for marijuana metabolites.
The suspension prevents Bonnar from coming out of retirement. He called an end to his professional fighting career a little more than two weeks after suffering a first-round TKO on Oct. 13 to middleweight champion Anderson Silva in Rio de Janeiro.
"The suspension came from a fight when he wasn't retired," Ratner said. "He's retired now but, like all athletes, suppose he wants to come back in three months?
"He's suspended for a year. He can't come back, no matter what. He says he's retired, but if he changes his mind he still can't come back.
"The suspension has been reported to the Association of Boxing Commissions' website. It should be supported by all commissions around the country."
UFC has not handed down punishment for Herman, but expects to do so within days.
Herman was submitted in the second round by former UFC interim heavyweight champion Antonio Rodrigo Nogueira.
"We'll have a decision on (Herman) by the end of this week," Ratner said. "We want to communicate with him about rehabilitation.
"We feel that performance-enhancing drugs are in a much different category than recreation drugs."