Toulouse forward Trevor Brennan has been banned for life from playing rugby after being found guilty of assaulting a supporter at a Heineken Cup game.
Brennan struck Patrick Bamford during the game in January
Brennan has also been fined more than £17,000 by the European Rugby Cup (ERC) arising from the incident in the game against Ulster in January.
He must also pay more than £3,000 compensation to the fan and to pay the costs of convening the hearing.
Brennan has also been banned from any involvement in future ERC competitions.
The 33-year-old, who did not attend Friday's hearing, has been hit by the penalties despite announcing his retirement from the game earlier this week.
Brennan, who earned 13 Ireland caps, was accused of entering a seating area during a match against Ulster at Stade Ernest Wallon on 21 January and punching the supporter Patrick Bamford.
The committee could not envisage more serious misconduct in relation to spectators and believed that the maximum permissible suspension was appropriate
Within days, the player, who claimed he had been provoked by chants, launched High Court proceedings against a disciplinary hearing on grounds its outcome could prejudice any criminal proceedings in France.
The player finally agreed to attend a preliminary hearing, which ruled a full inquiry would go ahead on Friday in London.
Last month the French Rugby Federation banned the player until 15 March, the day before Friday's hearing.
The independent disciplinary committee was chaired by HHJ Jeff Blackett (England) and included Rod McKenzie (Scotland) and Achille Reali (Italy).
An ERC statement said that the committee had "found Mr Brennan guilty of misconduct under the Heineken Cup disciplinary rules in that he entered one of the seating areas in the stadium and repeatedly struck an Ulster supporter namely Mr Patrick Bamford".
"It was the view of the committee that Mr Brennan's behaviour was completely unjustified and that he caused serious harm to an innocent spectator and significant damage to the image of Rugby Union," added the ERC statement.
I welcome the findings of the ERC organisation
"The committee could not envisage more serious misconduct in relation to spectators and believed that the maximum permissible suspension was appropriate."
On 1 February, fellow Toulouse player Gareth Thomas appeared before the committee to answer a misconduct complaint arising from the same match and was handed a four-week suspension and fined £5,000.
The Welsh international was found guilty of aggressively attempting to enter one of the seating areas of the stadium and of making an offensive hand gesture toward spectators.
In a statement, Bamford said he welcomed "the findings of the ERC organisation following their full and thorough investigation into the conduct of Trevor Brennan".
Mr Bamford is also taking libel action against a number of news organisations which reported on the incident.