Linfield have given a lifetime ban to an "individual" convicted of a criminal offence committed during the Champions League tie at Celtic on 19 July.
Linfield said the person was not a club member or season ticket holder.
"We have begun an investigation to establish how they were able to obtain a match ticket," the club added.
Celtic, who won the game 4-0 to complete a 6-0 aggregate victory, have been charged by Uefa over an "illicit banner" displayed during the match.
A Uefa spokesperson said that the charge related to the banner "portraying a person in a paramilitary uniform".
That case will be dealt with by the Uefa control, ethics and disciplinary body on Friday.
Trouble in the first leg in Belfast led to Linfield being handed a partial stadium closure for their next European tie and fined £8,850 following incidents at Windsor Park.
Uefa imposed the penalties after objects were thrown at Celtic players in the second-round qualifier.
Linfield's South Stand lower section 1 will be closed for one European game.
"We continue to co-operate with the PSNI [Police Service of Northern Ireland] over the events of the first leg and are hopeful that individuals who have now been identified will shortly appear before the courts," Linfield said.
"Linfield note that the local courts have the power to issue banning orders against individuals convicted of criminal offences in football stadia and would be fully supportive of such punishments being invoked in the event of convictions arising from this match."
Celtic's Leigh Griffiths received a one-match ban for provoking spectators while his club were fined £4,000. Griffiths tied a Celtic scarf to a goalpost after the final whistle in Belfast.