Fagerson was handed the ban, which rules him out of both 1872 Cup meetings with Edinburgh over the next two weeks, following an "independent disciplinary hearing" in London today after he was sent off by English referee Wayne Barnes in the 80th minute of the match for striking the La Rochelle replacement prop, Danny Priso. His leading left elbow strike resulted in a try by lock Scott Cummings, which appeared to have levelled up a tense clash in poor weather and leave stand-off Adam Hastings with a difficult touchline opportunity to win the match,
The red card ruled that out and effectively ended Glasgow's chances of progressing out of Pool 2 into the quarter-finals of Europe's elite competition.
The statement from European Professional Club Rugby said the offence related to "Law 9.12 Striking with the arm". Under World Rugby’s Sanctions for Foul Play, Law 9.12 relating to striking with the arm carries the sanctions of "low end two weeks; mid-range six weeks; top end ten to 52 weeks."
The committee consisting of Gareth Graham (England), chair,Val Toma (Romania) and Yannick Jauzion (France), considered video evidence of the incident and heard evidence and submissions from Fagerson himself, who accepted the red card decision. Glasgow Warriors team manager, Kenny Brown and EPCR disciplinary officer, Liam McTiernan also made submissions.
The statement continued: "The committee upheld the red card decision, finding that Fagerson had made contact with Priso’s neck in a dangerous manner. It then decided that the offence was at the mid-range of World Rugby’s sanctions and selected six weeks as the appropriate entry point.
"There were no aggravating factors, and taking into account the player’s guilty plea, clear disciplinary record and expression of remorse, the committee reduced the sanction by the maximum of 50 per cent before imposing a three-week suspension."
Fagerson will also miss the away match against Benetton in Treviso on 4 January before being available again for the 11 January home Heineken Champions Cup meeting with pool leaders Exeter Chiefs.