Steven Kelsey, now 63, sexually abused three children several decades ago when he was a juvenile.
Despite pleading guilty to numerous counts of indecent assault, he walked free from the dock.
The judge described the it as one of the most tragic cases he had ever heard.
But he said he was limited in the sentence he could pass because Kelsey could only be dealt with according to the law at the time he committed the “dreadful” crimes.
The maximum then for indecent assault was just six months prison.
Judge Christoper Smith said: “However unjust that must seem to an outside observer I must follow the law as it stood then.”
Emotional testimonies by each of Kelsey’s victims were read in court.
Judge Smith said a teenager sitting in the dock today for such offences would expect to go to prison for quite a long time.
He said: “This is without doubt one of the most tragic cases I have heard for many years.”
But he said if Kelsey, who the court heard had shown remorse, was jailed he would be released within weeks and that there would be a “worrying lack” of supervision from the probation service afterwards.
Instead he sentenced him to a three-year community order with supervision and 30 rehabilitation days.
Kelsey, now of Canwick Road, Lincoln, was also put on the sex offenders’ register for 10 years, made the subject of a sexual harm prevention order for the same length and given an indefinite restraining order against the victims.