The South African Rugby Players Association (SARPA) will challenge the decision of the rugby administration in South Africa that no overseas-based players will in future be eligible for national selection.
The South African Rugby Union (SARU) decided last week that players basing themselves in Europe will no longer come into contention for the Springbok rugby team.
Several top Springbok players, among them captain John Smit, lock Victor Matfield, hooker Gary Botha and wing Ashwin Willemse, have already signed up to play for clubs in France and England, with a further estimated 100 South African players based in Europe.
The players have cited the uncertainty of the succession plan of coach Jake White, whose contract with SARU expires after the World Cup, as one of the reasons for opting to play rugby in Europe from next season.
Also, many of the players were under the impression they could ply their trade abroad and still come into contention for the 'Bok side after White had selected overseas-based players Percy Montgomery, Jaco van der Westhuyzen, Danie Coetzee and Cobus Visagie.
According to SARU president Oregan Hoskins, blocking the players' availability for the Springbok team was the only way the rugby administration in the country could halt the exodus of players to the northern hemisphere.
But SARPA now want to legally challenge the decision on the basis of a restriction of trade, according to the Johannesburg-based Sunday Independent newspaper.
The union claims that the players were never informed about the decision and that they were never consulted about it.
SARPA chairman Hennie le Roux called the decision to ban overseas-based players from turning out for the 'Boks "ridiculous," according to a report in the Afrikaans Sunday paper Rapport.
The message that was being sent out to the 'Boks, just weeks before the World Cup was, according to Le Roux, "you can no longer play for the 'Boks if you've got a contract outside South Africa's borders, but for now please win us the World Cup."
Gary Botha, understudy to 'Bok captain Smit, told Rapport he was left with no choice but to seek employment elsewhere.
"Nothing means more to me than the 'Bok jersey, but as a father I need to put food on the table," he said.