(CNN) -- California horse-racing authorities handed the trainer of Triple Crown hopeful I'll Have Another a 45-day suspension Thursday stemming from a 2010 race with another horse, but cleared him of giving that horse an energy-boosting cocktail.
The suspension won't take effect until at least July 1, meaning trainer Doug O'Neill will be able to participate in the June 9 Belmont Stakes -- when Kentucky Derby and Preakness winner I'll Have Another is carrying high hopes for the sport's first Triple Crown since 1978. And the California Horse Racing Board's decision explicitly cleared O'Neill of "milkshaking" the throughbred Argenta during a race at southern California's Del Mar track in September 2010.
The board did find O'Neill, as Argenta's trainer, was responsible for high total carbon dioxide levels found in its blood -- a sign a horse might have been given a "milkshake" of baking soda, electrolytes and sugar believed to help it combat fatigue. It fined him $15,000, and said another 135 days of suspension could be applied if O'Neill is found to have violated other rules in any jurisdiction.
But a state hearing officer found no sign of any "intentional acts" on the part of the trainer or any sign that betting on the race had been skewed toward Argenta, which finished well out of the money in eighth place.
O'Neill can challenge the finding in court, but his brother, Dennis O'Neill, said no decision has been made on how to proceed.
"We're just ecstatic that the judge ruled we didn't do anything to make the TCO2 (total carbon dioxide) level go up," Dennis O'Neill told CNN. But he said there was "absolutely" no doubt his brother would be able to take part in the Belmont, in New York.
"We're very happy that the press release is very clear that Doug never milkshaked the horse, and there was no suspicious betting pattern," he added.
Lee Park, a spokesman for the New York State Racing and Wagering Board, said that agency would review California's decision. But since the suspension won't take effect until July, "it should have no bearing on the June 9 Belmont Stakes," he said.
The 2010 allegation isn't the first scrape O'Neill has had with California regulators. In 2007, he was fined $3,000 after another horse showed high carbon dioxide levels. And in 2010, the Illinois Racing Board suspended him for 15 days when another horse showed high blood CO2 levels; California's racing board issued him a matching suspension.
But there have been no allegations that O'Neill had given a milkshake to I'll Have Another. And his brother told CNN earlier this week that "We've never milkshaked a horse."
"We wouldn't know how to do it," Dennis O"Neill said. "It's never been done by us or anybody in the barn."