The Olympic eligibility loophole that allows players to swap nations may be closed to heavier athletes and any others the IRB arbitrarily decide are not genuine candidates to play sevens at Rio.
The game's governing body, conscious they have paved the way for players to once again represent two nations in a career, will use an as-yet unspecified committee to determine who will and won't be allowed to switch allegiance.
This subjective approach is being used amid concerns that sevens events over the next two years could be abused by players who have no real intention or desire to play the abbreviated game. As a result of sevens being in the next Olympics, different eligibility laws will apply.
As the Herald on Sunday reported recently, players whose eligibility has been captured by one nation will be able to represent another if they hold the relevant passport.
All they will have to do is play one sevens tournament in 2015 or 2016 designated as an Olympic qualifying event.
If they do that, they will become eligible for that new nation at all levels of the game as long as they haven't played test rugby for their original nation in the past 18 months.
But now that several nations have sought clarity around the detail - and asked whether individuals need to be in the squad or get on the field at a sevens tournament to satisfy the criteria - the IRB are suggesting no one whose eligibility has already been captured will be allowed to be selected until they have approval.
That will be granted by the IRB on the basis they have to be convinced the player in question is a genuine prospect of representing his 'new' nation at the Olympics. If they suspect the athlete is using sevens to become eligible in the 15-a-side game, they will reject the application.
While it's understandable the IRB don't want the credibility of their sevens tournaments damaged, there are concerns about the assessment policy being discriminatory and challenged in law.
It may be easy enough to say somebody such as Isaia Toeava would be a genuine candidate to play sevens for Samoa at the Olympics and former All Blacks prop Neemia Tialata wouldn't be.
But what about a mobile and gifted ball-player such as former All Black John Afoa? He's 125kg but could just about handle himself in the short form of the game. Or what about someone such as Chris Masoe, who has significant sevens experience but is a 110kg loose forward?
Then there is the secondary issue of finding an IRB panel that is not conflicted. Most nations would have some kind of vested interest in the outcome of these decisions.
Scotland, for instance, are in Samoa's 2015 World Cup pool. Would any Scots on the panel be in favour of seeing Samoa strengthened by the inclusion of the likes of Toeava, Afoa, Tialata and Masoe?
New Zealand Rugby Union chief executive Steve Tew is involved with the IRB committee assigned to eligibility matters. He says he aired concerns about the potential conflict of interests that may arise but also stressed that no one is expecting significant numbers of players trying to switch allegiance.
"We have tried to ensure as closely as we can that we adhere to the principle of the one-country rule," Tew said. "With regards to the terms of the IOC rulings which are more flexible, we remain committed to the principle of players representing a country with whom they have a genuine and authentic link."