Hours after Nevada disallowed fighters from therapeutic-use exemptions for testosterone,
Former light-heavyweight champion Lyoto Machida will now fight Weidman at the MGM Grand.
The 36-year-old Belfort (24-10), who last had a title shot against then-middleweight champion Anderson Silva in 2011 and has fought in the UFC since 1997, has used testosterone replacement therapy (TRT) in recent fights.
In a statement, the UFC said, "Belfort ... recognizes that he needs an extended period of time to become
licensed in the state of Nevada. With the event scheduled to go on sale shortly, Belfort agreed to withdraw from the fight in order to allow the UFC's promotional efforts to move forward on time."
The past allowance of TRT has been criticized given the performance-enhancing effects of testosterone, and the ability of athletes to secure prescriptions of questionable credibility.
Belfort was suspended for nine months by Nevada in 2006 for testosterone use, and after three consecutive wins propelled him to the title shot, Nevada officials were watching his case closely.
Belfort said in late December, after Weidman beat Silva for a second time, that he was confident he could fight in Nevada, but declined to express his interest in requiring TRT.
"I'm able to fight anywhere, I have done everything by the book," Belfort said. "Everybody knows that people cheat, but I don't."
Nevada on Thursday afternoon banned the practice, and UFC President Dana White issued a statement
supporting the move.
"We believe our athletes should compete based on their natural abilities and on an even playing field," White said. "We also intend to honor this ruling in international markets where, due to a lack of governing bodies, the UFC oversees regulatory efforts for our live events. We encourage all athletic commissions to adopt this ruling."
At 10:30 p.m. Pacific time, the UFC announced Belfort was out of the Weidman fight.
The 35-year-old karate expert Machida (21-4) has beaten Mark Munoz and Gegard Mousasi to gain the title shot after losing the belt to Mauricio "Shogun" Rua in 2010 following a title win over Rashad Evans. Machida lost by second-round submission in a 2011 title bout to current light-heavyweight champion Jon Jones.
Machida trains with Silva and will attempt to become just the third fighter to win titles in two divisions.