'Parliament has deprived the courts of any power of detention of a person of this age or of what many people might think was any effective punishment for that grave crime,' Judge Bruce Laughland said at the Old Bailey.
He conceded he did not have the power to pass the sentence of three months' detention which he imposed on the 13-year-old east London boy last week. 'I revoke it,' he said. 'I substitute the most that Parliament allows - that he be placed under a supervision order for a year and undergo 90 days of supervised activities.'
Judge Laughland said the boy, together with two older boys, had kidnapped the 14-year-old and taken him to Epping Forest.
'There he was subjected to a terrifying experience which included this defendant carving his initials on his body,' he said.
A child under the age of 14, however dangerous and however heinous the crime, could not be locked up for anything short of homicide.
'The responsibility for what might occur by letting such dangerous children at liberty is the responsibility of Parliament,' the judge said.
The schoolboy pleaded guilty last week to false imprisonment and wounding. Two youths were jailed for two years and 18 months.
Their victim, the court was told, had his hair pulled out, his hands slashed, was whipped with a studded belt and beaten until he became unconscious.
The 13-year-old burned his chest with lighted cigarettes and cut the letter 'M' into the boy's back. The attackers were said to be taking revenge on the 14-year-old because he was a bully.