Kevin Stamp, 25, who was accused of assault causing bodily harm in the washroom of a St. John's bar in 2012, was found not guilty in provincial court on Friday.
Judge Pamela Goulding ruled that Stamp had acted in self-defence during an incident at the Shamrock City bar on Water Street in late 2012.
Stamp had testified during the trial that when another man sexually assaulted him by grabbing his penis, he head-butted him.
The man's nose was broken, and a gash on his forehead had to be stitched.
The Crown maintained that the incident was an unprovoked attempt, but Stamp said he had cause to act.
"The man came in and said, 'I'd like to see your with your pants off,' and he grabbed my [penis]. I didn't think about it and say, 'I'll do this or this' — I instinctively head-butted him," said Stamp.
'Highly unusual, even bizarre'
In court on Friday, Goulding said she found the story the alleged victim told about an unprovoked attack "highly unusual, even bizarre."
'I accept he acted instinctively to repel the attack' - Judge Pamela Goulding
Goulding said there was an air of reality to Stamp's account, and accepted his testimony that he was defending himself.
The Crown had asked why Stamp didn't go to the police if he had been sexually assaulted, given that he had told others about it.
Stamp testified that he was embarrassed.
The judge added, "There are many reasons why a victim of a crime doesn't report it, even if acquaintances might know."
Goulding said that Stamp was sexually assaulted and had the right to defend himself.
"I accept he acted instinctively to repel the attack," she said.
The Crown argued that even if the sexual assault occurred, Stamp used too much force. Goulding disagreed.
"He cannot be expected to weight the niceties of the amount of force he used," Goulding said.