Toulouse will face Munster in the Heineken Champions Cup this weekend without the services of key forward Rynhardt Elstadt.
The South Africa international returned home less than a fortnight ago to complete a commercial pilot's licence exam, with permission from the Top 14 club.
Elstadt underwent the 10-day isolation period on his return to France and missed the league meeting with Montpellier last Saturday.
However, the Irish government requires anyone returning from South Africa to quarantine for a 14-day period.
The Toulouse squad are due to travel to Ireland on Thursday which comes 12 days after Elstadt's return, meaning that he has to be ruled out.
"There was provision for rest but the period is obviously not conducive to going to the beach," said Toulouse head coach Ugo Mola.
"He had an exam to complete to become an airline pilot and was allowed to leave, with the understanding that would have to honour the French Health Ministry’s 10-day isolation rule.
"But we have received the new EPCR regulation which adapts to the Irish government which prohibits its coming."
#MUNST, Ugo #Mola : "Rynhardt Elstadt avait un examen de pilote de ligne en Afrique du Sud. Il y est allé en accord avec les règles gouvernementales.
Il est rentré, a respecté une septaine et s'est entraîné mais les règles irlandaises ne lui permettent pas de jouer ce week-end."
— Stade Toulousain (@StadeToulousain) March 31, 2021
Mola also revealed that the club requested an exemption from the Irish government for Elstatdt and assistant backs coach Alan-Basson Zondagh, who also returned to South Africa during the Top 14 break, but they were turned down.
Centre Pita Ahki and wing Yoann Huget ( both Achilles) could also be added to the long list of absentees but the decision on their participation will be made on Thursday.
Toulouse are already without wings Lucas Tauzin and Juan Mallia, full-backs Thomas Ramos and Arthur Bonneval, and centres Pierre Fouyssac and Sofiane Guitoune.
Second row Joe Tekori was due to face a Top 14 disciplinary panel on Wednesday after he was cited for an incident in Saturday's match against Montpellier.
Meanwhile, Munster captain Peter O'Mahony is a doubt for the last 16 clash after he sustained a deep laceration to his thigh during last weekend's defeat to Leinster in the Guinness PRO14 final at the RDS.
Munster head coach Johann van Graan said after the game that O'Mahony was "struggling" and that it "didn’t look good."