New research from the University of Oslo claims athletes who take anabolic steroids can retain muscle development advantages for decades.
But Travis Tygart, chief executive of the United States Anti-Doping Agency, still believes athletes banned for doping offences should be handed second chances.
US sprinter Gatlin is 2014’s fastest man, and has remained a controversial figure since his return from his second ban in 2011.
“If somebody commits a violation, serves a ban and comes back to the sport, part of the rule is this idea of redemption,” Tygart told BBC Sport.
“There is some recent science on the effect of steroids on mice, but there is no proof yet it translates to humans,” said Tygart, who in 2012 declared the “conclusive and undeniable proof” that American cyclist Armstrong was a drug cheat who was at the heart of a team-run doping conspiracy.
“We’ve looked at it and you have to be cautious about changing the goalposts in the middle of the game based on a few sound-bites in the press from one paper on mice.
“That’s not fair. What’s fair, and what athletes and the public rely on, is a set of rules that are enforced evenly.”
Lord Coe admitted he had a “big problem” with Gatlin earlier this week, supporting the Oslo study’s claims over long-term residual benefits for athletes after drug use.
The International Association of Athletics Federations (IAAF) vice-president told London’s Securing Sport conference: “The only thing I would say is that he is entitled to be competing. I’m not particularly comfortable about it. I think you’d be pretty surprised if I did sit here and was sanguine about that.
“I personally have big problems with that.”
Tygart however believes academic studies are yet to prove links to long-term drug effects in humans, rather than mice.
A new World Anti-Doping Code will be enforced from January 1, 2015, extending first-time bans from two to tour years, ensuring guilty athletes will miss at least one Olympic meeting.
“Fairness dictates that we stick to the rules, but if the science says we have to change the rules then, absolutely, let’s do that,” said Tygart.