In a shock move, Hayne quit the NFL on Monday morning to attempt to earn selection with Fiji in rugby sevens at the Games.
However Ings said World Rugby rules require players to be in a registered testing pool for six months to be eligible to compete at sanctioned competitions.
And according to the former ASADA chief, Hayne’s stint in the NFL does not fit the requirements.
“If Jarryd Hayne had been playing in WADA compliant sport he would have grounds to reduce the 6 months,” Ings tweeted on Monday morning.
“But NFL is PED badlands. No chance.”
Ultimately, the decision on whether Hayne would be cleared to play will come down to the International Rugby Board, while the former NRL star could appeal any decision which goes against him.
But Ings believes the restriction is a vital one.
“The six-month return to competition rule is standard across most sports for athletes returning to international competition. And necessary,” Ings tweeted
“The rule equally applies to reinstatement or to new players. Sensibly it must or any NFL player could bulk up and play.”
Hayne’s hopes of being cleared to play should increase though given fellow NFL-convert Nate Ebner debuted for the United States at last month’s Singapore World Sevens tournament – just a month after he left the New England Patriots.
Ings, who was chief of ASADA for six years, also indicated similar rules apply to the NRL.
Hayne fly to London today to join up with the Fiji rugby sevens team for their final leg of the World Series, in a desperate bid to earn selection for this year’s Olympic Games in Rio de Janeiro.
Although he did not mention a return to the NRL, that now seems a realistic option for the 28-year-old.
“I am retiring from the NFL because the Fiji rugby sevens team reached out to me about the opportunity to join the team for the upcoming Olympics, and I simply could not pass that chance up,” Hayne said in a statement.
“The Olympics has been something I have admired since I was a little boy, and it is an opportunity I feel very similar to me joining the NFL.”
Hayne met with the Fijian Sevens side ahead of the Sydney leg of the series in February, and it was there that the dream of Olympic representation was first broached.
However his place in the squad for Rio is not guaranteed, according to Fijian coach Ben Ryan.
“I have no promises he is going to make the 12, but we will see how he goes,” Ryan said.
“He will then come into Fijian camp for the Olympic period.
“It is a huge challenge for Jarryd but if he gets into the squad it is only going to be on form, because he is a blinding rugby player.”
Hayne has often talked about his deep connection to Fiji and his life-changing experience with the Fiji team at the 2008 Rugby League World Cup.
While born and raised in Sydney, Hayne’s father, former South Sydney Rabbitohs centre Manoa Thompson, was born in Fiji.
Hayne became a devout Christian through his experience with Fiji in 2008, a period he said “changed my life”.
Hayne’s NFL exit came as almost as big of a shock as his announcement at the end of 2014 he was quitting the Parramatta Eels for American football.
Big spending NRL teams, including the Sydney Roosters, are expected to attempt to try to entice him back to rugby league.
Hayne has spent the past six weeks training under new 49ers head coach Chip Kelly and was considered a good chance to fit into a new high-speed offence as a running back and punt and kick returner on special teams.
“Jarryd is a tremendous example of what can happen when you commit to a goal and do everything in your power to make it a reality,” 49ers general manager Trent Baalke said.
“He earned the right to wear a 49ers uniform and compete alongside the best in the game.”
Hayne originally signed with the 49ers as an undrafted free agent on March 3, 2015 and appeared in eight games last season.
“I could not have predicted how far I have come as an NFL player,” Hayne said.
“To not only be able to play in a game but also say that I started a game in the NFL is something that I will remember for a lifetime.”
He had 17 carries for 52 yards along with six receptions for 27 yards. He also returned eight punts for 76 yards on special teams, but midway through the season was waived and then signed to the practice squad.
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