Wales scrumhalf Rhys Webb will be ineligible to play for the national team next season under new selection policy guidelines introduced on Monday.
Any player taking up a new contract outside Wales must have won 60 caps or more to be eligible to play for the country, the Welsh Rugby Union said.
It follows a criteria already used by Australia for selecting individuals at Test level who do not play domestic rugby in their own country.
Webb, who has signed to play for French giants Toulon from next season, has 28 caps for Wales.
"He can still get out of his Toulon contract," Wales coach Warren Gatland said. "He has just signed a letter of agreement. He has not signed a full contact with Toulon. He needs to make his own decision.
"You have to feel for him. From my point of view, we potentially won't be able to pick a world-class player. That's disappointing."
Previously, players at clubs outside Wales required one of four wildcard picks from Gatland to represent their country, with that figure dropping to two for the 2019-20 Rugby World Cup season.
Players already playing outside Wales will be exempt from the new policy.
Wales flyhalf Dan Biggar will join English team Northampton next season. He has 56 caps and is likely to reach 60 this season, with Wales having four autumn Tests, including a November 11 date against Australia, then a Six Nations campaign.
George North, Jamie Roberts and Taulupe Faletau all play outside Wales and have more than 60 caps. Fullback Liam Williams had already started playing for Saracens in England before the policy changed.
"The number means that when those players do reach 60 caps, there is an opportunity to go and play outside of Wales. I understand that," Gatland said. "There is pressure on players to make what is the best decision for themselves and in the future. We have to recognise that. There are market forces outside of Wales.
"Part of the criteria is a desire to have five competitive entities - the national team and four competitive regions."