The region will also review stewarding arrangements in that part of Stradey.
"I have seen video footage of the incident and I'm shocked and disgusted at what I saw," Gallacher said. "We are confident that we will be able to identify the fan, who will not be welcome at Stradey Park again."
Blues Chief executive Robert Norster welcomed the tough stance taken by their Welsh regional rivals. "The safety of players, officials and spectators is of paramount importance to us and we are encouraged to hear that the Scarlets also share this view," Norster said. "We fully support their actions in trying to identify and ban the person responsible for last night's incident."