Former boxing world champion Joe Cordina was acquitted of assaulting a man he punched outside a petrol station.
The incident at a garage in Pentwyn, Cardiff, in February led to the 34-year-old being denied entry to the United States for a WBO lightweight title fight.
District Judge Charlotte Murphy found Cordina not guilty of assault by beating against Jamie O’Brien, 33, following a trial at Cardiff Magistrates’ Court.
She said she was satisfied Cordina believed it was necessary to use force to defend himself.
“I am further satisfied that a single, measured, controlled punch was proportionate in the circumstances,” she said.
“It is very easy to consider the defendant’s response by considering the CCTV in slow motion, however the defendant had a split second to consider his response to the shoulder barge.”
Cordina had been filling his Land Rover with fuel before approaching O’Brien, who was sitting on the pavement near the petrol station exit.
CCTV footage showed O’Brien pushing Cordina with his shoulder before the two-time IBF super-featherweight champion punched him hard enough to knock him to the ground.
The two men then continued arguing and exchanged further blows.
O’Brien, who is also from Pentwyn, had previously pleaded guilty to assault by beating.
Police began investigating the incident after footage of the altercation was circulated online.