Mike Tyson and Roy Jones Jr are yet to be officially drug tested ahead of their upcoming exhibition bout.
The faded legends are due to meet in California on September 12 over eight 'friendly' rounds.
Neither former world champion will be allowed to hurt the other while there will be no judges and no official winner.
The California commission are willing to sanction the fight on the understanding it is stopped if it escalates beyond a 'sparring session'.
The referee will also be permitted to step in should either fighter be cut.
But according to The Ring magazine, talks between the Voluntary Anti-Doping Association (VADA) and the fighters remain ongoing, despite the fight being little over a month away.
And a source told the outlet : "Drug testing is the major concern for this event. That needs to be the focus, not the size of the gloves, or the headgear."
Tyson and Jones are not expected to wear headgear for the bout and will wear 10oz gloves rather than the 8oz versions worn by professional fighters.
But despite the rules in place, both men expect a 'proper' fight.
Tyson said recently: "If the opportunity comes [for the knockout], I'm always looking for it.
"This is search and destroy and I'm looking forward to recapturing my glory."
Jones, meanwhile, said: "I understand because Mike doesn't just look like a killer he is a killer," he said.
"If Mike doesn't kill quick he's fighting one of the smartest savviest guys to ever do the thing, if he don't kill quick he's in trouble. 'If you don't kill right away what are you going to do? I seen all those smoking videos don't think I don't know what's going on, I'm not stupid."
The fight will be held behind closed doors due to the coronavirus crisis with fans asked to splash out $50 to watch the fight on pay-per-view in America.
No broadcast details have been announced for fans in the UK.
