Munster fly-half Ronan O'Gara has been cited for kicking an opponent during Sunday's 26-17 victory over Edinburgh in the Heineken Cup.
The 35-year-old Irishman was reported by citing commissioner Alberto Recaldini after a second-half incident involving Edinburgh lock Sean Cox.
If found guilty, O'Gara could find himself banned for some or all of Ireland's Six Nations campaign, which begins at holders Wales on February 13.
The citing carries a low end entry point of a four-week ban, with a top-end sanction of anywhere between 12 weeks and a year if found guilty.
Meanwhile, Racing Metro's France international centre Fabrice Estebanez has also been cited for allegedly striking Saracens wing David Strettle with his arm during his side's loss on Saturday.
Stade Francais lock Juan Cruz Guillemain faces a more serious charge under the same law after allegedly striking Grenoble's Fabien Alexandre with his head in their Amlin Challenge Cup match.
The top-end entry point for Guillemain's citing is from 16 weeks to two years.
All three cases will be heard in Dublin on Thursday, with Judge Jeff Blackett passing judgement on O'Gara, while Ireland's independent Judicial Officer Pat Barriscale will rule on both Estebanez and Guillemain.