The International Rugby Board has insisted it was prepared to impose "significant sanctions" if it found examples of players being prevented from representing their country.
The global governing body said it would be keeping a close eye on the issue during this month's international matches in Europe in the wake of former Racing Metro backs coach Simon Mannix's allegations that the French club paid players to not be available from the Fiji World Cup squad.
The FRU confirmed on Thursday it has officially complained to Racing Metro over Jone Qovu's unavailability for Fiji's current European tour. Qovu refused selection claiming to be injured, but later played a club match.
FRU spokeswoman Talei Mow said the union would make a statement later this week indicating whether it would alert the IRB to the issue. Chief executive Manasa Barivilala is currently in England with the Fiji team.
IRB Regulation 9 forbids clubs from offering disincentives, either through "contract or conduct", to players to represent their country but critics insist officials have not done enough to enforce the rule.
But in a statement issued from its Dublin headquarters, ahead of an opening weekend of November Tests including England's match with Fiji at Twickenham, the IRB said it would act on breaches of regulation nine.
"Player release is central to the integrity and economic sustainability of the international game and the IRB continues to be proactively committed to assisting (national) unions with player release issues when requested by them to do so under regulation nine," the statement said.
"The regulation is designed to deliver a fair, equitable and proportionate framework for facilitating the release of the world's best players for international duty within designated windows without impediment irrespective of country of employment.
"This regulation goes to the very core of supporting the integrity of the international game.
"The IRB takes any breach of the regulation very seriously and acts on release issues where it is formally requested to do so by a union or if it is presented with credible evidence provided by a union or recognised rugby body that would allow it to pursue its own enquiry," the statement added.
"Unions also have a clear obligation to do everything possible to uphold the regulation within their territory or they risk significant sanctions.
The IRB also said the subject of "release issues" during this month's internationals would be on the agenda for their November meetings in Dublin.