The International Rugby league will introduce a great-grandparent rule which will allow players to represent their heritage going back three generations.
In a move aimed at ensuring a deep enough player pool for smaller nations, world officials have agreed to a move that will increase eligibility by an extra generation.
Under the terms of the rule, players will be eligible to play for a nation if any of their eight great grandparents were born in that country.
It is unclear how many players will now be able to represent different countries under the new structure.
Most other sports allow a grandparent rule for eligibility, including both soccer and rugby union.
This year's World Cup has easily been the most attended in the game's history based on average crowds, with the rise of Pasifika players representing their heritage largely credited for that.
The change comes after Cook Islands coach Karmichael Hunt had called for broader eligibility, with the nation's population having fallen from above 20,000 in the 1970s to below 14,000 now.
"We all live in Australia or New Zealand," Hunt said last week.
"There are a lot of great grandparents that have Cook Islands kids playing in good systems in Queensland and NSW and we'd love to get access to those and hopefully we can get a decision in our favour.
"If you want to identify and represent your Cook Island heritage and you have got that in your blood you should have the right to do that."
"From all reports (Canberra fullback) Kaeo Weekes has grandparents that are Kukis or he has Cook Islands heritage.
"He is sitting on the couch watching the tournament right now. We want our best players playing in this competition."
The eligibility extension also comes with International Rugby League officials expected to announce the USA as the location of the 2030 World Cup on Monday.
