Martial arts fan William Thieu took a weapon to a street clash after his brother sent him a text message saying: "No rules."
When trouble broke out police responded to the incident and found the weapon - nunchucks - in the road where Thieu, 19, had thrown them.
No charges were made against his older brother, who had brought along a knuckle duster for the fight, which happened when he tried to stop elderly parents getting into their home.
Stephen Burdon, representing Thieu, said police officers turned up at the premises but then left. When the older brother threatened to damage the house, they declined to return.
"Police thought it was a civil issue and William decided he had to attend and got a message 'no rules.' He took along the nunchucks, which are a defensive weapon.
"He uses them as part of a martial arts discipline and had never taken them out of the house before.
"He is a young man who has made a mistake," said Mr Burdon on behalf of Thieu, of Honeywood Drive, Nottingham, who was given a six-month conditional discharge.
Thieu admitted having an offensive weapon on August 31 and must pay a government surcharge of £21. He had never been in trouble before.
Presiding magistrate Miriam Jackson told him: "These were clearly very difficult circumstances that evening. We know what you were doing was acting to defuse the situation. We hope things settle down."
The Nottingham Trent University business student replied: "Thank you very much."
Emma Wakefield, prosecuting, said police officers arrived to find the brothers "gesturing towards one another" in Rugby Close.
"Officers attempted to get him away from his brother and saw black nunchucks in the middle of the road.
"He said that he had them for self-defence and had them for two years to train like Bruce Lee," added Miss Wakefield.
