World Rugby has raised the residency period needed for Test eligibility from three to five years.
The amended rule, which comes into effect at the end of 2020, 'ensures that a player has a genuine, close, credible and established link with the nation of representation', according to World Rugby.
'This is an historic moment for the sport and a great step towards protecting the integrity, ethos and stature of international rugby,' World Rugby vice-chairman Agustín Pichot said.
'National team representation is the reward for devoting your career, your rugby life, to your nation and these amendments will ensure that the international arena is full of players devoted to their nation, who got there on merit.'
World Rugby also announced that unions may no longer nominate their U20 team as their next senior national representative team (effective 1 January 2018).
The Junior Boks are currently SA Rugby's next senior national representative team, which means anyone who plays for them is tied to South Africa and cannot represent another country.
From next year, though, that will no longer be the case, with the South Africa A side likely to become SA Rugby's next senior national representative team.
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