At Friday's weigh-in, Cormier arrived to the scale just minutes before a two-hour window ended and initially weighed 206.2 pounds, which is 1.2 pounds over the allowable limit.
After missing weight, he walked behind a curtain that was set up in the room. He emerged moments later to step back on the scale and weigh in at 205 pounds.
Officials from the New York State Athletic Commission approved Cormier's weight at 205. Johnson (22-5) weighed in moments later at 203.8 pounds.
In most jurisdictions, a fighter is not allowed to re-weigh after missing weight on the official scale. NYSAC executive officer Tony Giardina told reporters that NYSAC policy allows a second weigh-in for title fights.
"The policy of the athletic commission in championship bouts is to allow a fighter to get on the scale a second time if they are overweight the first time," Giardina said. "He came in 1.2 pounds overweight. He's allowed, according to commission policy, up to two hours to get back on the scale. He came back a short time after, and he re-weighed exactly 205 pounds.
"So according to commission policy, it's a legal weigh-in."
Asked where the policy is written, Giardina said it's not a part of the state's statutes but a "published policy." ESPN has not yet located a copy of the policy.
Cormier (18-1), who cuts a good amount of weight to compete at 205 pounds, might have used an old wrestling trick to lose 1.2 pounds in such a short amount of time.
During the second weigh-in, UFC officials held a towel out in front of Cormier, who had stripped off all his clothes. Cormier clearly pushed down on the towels, which would presumably offset his weight slightly.
Giardina said commission officials did not notice Cormier's hands on the towel.
"I didn't see that," Giardina said.
Johnson has not commented on the weigh-in; he happily left the room after making weight. Had Cormier missed weight, the bout would probably have gone on but would not have been an official title defense for Cormier.
Had Cormier missed weight and the fight still happened, Johnson would have been due a percentage of Cormier's fight purse.
Johnson's manager, Ali Abdelaziz, told ESPN he had reviewed film of the weigh-in and would evaluate it further after Saturday. For now, he said the team's focus is on winning the fight.
"Right now, we're treating this as nothing," Abdelaziz said. "We're fighting the best in Daniel Cormier and we're treating it as he made weight. We want Anthony to have positive energy.
"If anything went wrong [at the weigh-in], it will be resolved after the fight. I will say it was an abnormal weigh-in. But right now, as far as I know, they both made weight and may the best man win."
Saturday's fight is a rematch of a UFC 187 bout in which Cormier submitted Johnson in the third round to win the vacant UFC light heavyweight championship.
Both fighters can expect to be watched closely by former light heavyweight champion Jon Jones, who will be in the audience for Saturday's fight. In a 25-minute news conference held in Buffalo, Jones said he is focusing solely on reclaiming the title he has lost twice because of suspensions.
He also accused Cormier of being "dishonest" at his weigh-in.
"That was absolutely nuts. I couldn't believe what I was witnessing," Jones said. "If you focus on his hands, you can see him looking down and like balancing out his weight just right to make 205 [pounds]. What a clever trick. Pretty dishonest of him.
"The crazy thing is that it was allowed to happen. I would imagine there would be some type of commission to go back and see this blatant foul play and address it. No one's addressed it. They just got away with doing one of the dirtiest things I've seen in sports."