Three naturalized Japanese citizens found themselves on the wrong side of a decision that essentially restricts their ability to work as professional rugby players in their adopted homeland.

The Japan Rugby Football Union on Friday confirmed that the three, including two who are eligible to play for Japan in the Olympics, will continue to be denied Japanese status within the Top League simply because they are not eligible to play for Japan's national rugby 15s side, the Brave Blossoms.

The purpose of the rule, passed in 2016, to restrict Japanese status to those eligible to play for the Brave Blossoms was, according to Top League Chairman Osamu Ota, to bolster the strength of the national team. The argument that it discriminates against Japanese citizens was not enough to sway the JRFU.

The ruling leaves former All Black Isaac Ross, ex-New Zealand sevens player Colin Bourke and former Australia sevens player Brackin Karauria-Henry to be treated as 'non-Japanese' in the Top League.

Both Karauria-Henry and Bourke are being considered for Japan's Olympics sevens team because the Olympic Charter defines a different set of eligibility conditions for naturalized citizens.

Ota said the ruling could not be changed immediately as "it was not possible for teams to change their budgets and contracts ahead of the new (Top League) season," which is set to start in January 2021.

The only thing the union did agree to change, for now, was the names of the player categories to remove any discriminatory terms such as Japanese, foreigner and Asian, and replace them with Category A, B, C etc.

"This does not affect the eligibility of the players and is nothing more than a cosmetic change," said a source who had knowledge of the meetings between the players and the union.

Ota said the rule would be reviewed before Japan's new league kicks off by early 2022, but that did not appease Ross. The 35-year-old became a citizen in 2017, having started the process in 2015 before the rule took effect.

The eight-time All Black was recently released by NTT Communications Shining Arcs after nine seasons, in part because his continued status as a non-Japanese means he only got limited playing time.

He is particularly upset that clubs are making use of the "eligible to play for Japan" status, even though many of those to whom it applies have no intention of playing for the national team.

World Rugby regulations state that a previously uncapped player must reside in a country for at least three years before they can play for it. But the JRFU deems anyone who has not played for another test team eligible for Japan.

"We had a player at NTT who was in Japan for just two years. He kept a Japanese player out of the starting team even though he himself was never going to play for Japan," said Ross. "And yet someone who has shown their commitment to Japan like me, has shown loyalty and benefited the Japanese game is being punished."

Hideki Niizuma, a lawmaker in the House of Councilors, said the ruling was wrong.

"It is unreasonable that a player with Japanese nationality due to naturalization must be registered as a foreign player just because he has a history of representing a foreign country," he wrote in an email.

The 50-year-old Komeito member, who played rugby at the University of Tokyo, said he would be seeking the opinion of "specialized agencies and experts such as the Japan Sports Law Association and the Japan Sports Arbitration Agency."

While Bourke and Karauria-Henry look set to carry on in a league run by a union that, as Bourke puts it, "sees me as a foreigner but at the same time Japanese enough" to play for the hosts at the next Olympics, Ross is forced to continue his career overseas.

"The JRFU's motto of 'One Team' and the Top League's 'For All' aren't consistent with their actions," he said.