Stephen Lawrence's killers would have faced double the amount of time behind bars if they had carried out the racist murder today, the Old Bailey trial judge said.
Mr Justice Treacy told Gary Dobson and David Norris: "In modern times an adult committing this crime would be facing a life sentence with a starting point for a minimum term of around 30 years."
But the judge was restricted by having to apply the law as it was at the time of the attack in 1993, a decade before tougher sentencing rules were brought in and when both men were still juveniles.
Dobson was given at least 15 years and two months behind bars while Norris was told he must serve at least 14 years and three months before being considered for release.
Michael Turner QC, vice-chairman of the Criminal Bar Association, warned against saying the tariffs, the minimum time they must spend in prison, were too light.
"Undoubtedly it would be higher now, but the judge has stuck really closely to the guidelines," he said.
"What I would be concerned about from the public's point of view is that, if we start saying these sentences are woefully low, the implication is that the judge has taken some kind of sympathy with the murderers and he has not at all."
He described Mr Justice Treacy, a member of the Sentencing Council which sets guidelines for judges, as "a very solid, safe pair of hands".
Mr Turner added that, if they are released, both men would be on a life licence and would be sent back to prison for any breach of their conditions or if they committed any other crimes.
"Given who they are, I would be surprised if they managed to survive particularly long out on a life licence," he said.
He added that judges "don't have a huge deal of discretion" in sentencing and their hands were tied by both statutory law and common sense.
While judges had some discretion and could decide how much significance they should attach to the fact that the killers evaded justice for almost 19 years, he urged against "retrospective sentencing".
Defendants should be sentenced according to the law as it stood when they committed the crime, he said.
Mr Turner also urged Parliament to "stop interfering in the sentencing process" by proscribing minimum terms by statute, adding that deterrent sentences do not work.
"If the sentence for parking on a double yellow line was life imprisonment, that will work," he said.
"But it does not for murder.
"Murderers are either terrorists, in other words professional killers, who would like to be hung so they can be martyrs, or one of the vast majority who are not thinking about it (sentencing) at all."
He went on: "If racism is endemic within society, it's not going to be cured by racist murderers being sent away for life."
As they were sentenced as juveniles, Dobson and Norris will technically be detained at Her Majesty's Pleasure, the form of murder sentence for under-18s.
Previously, the Home Secretary was responsible for determining the minimum term for offenders under this sentence.
But the law was changed in 2000 after a ruling by the European Court of Human Rights in the case of James Bulger's murderers, Jon Venables and Robert Thompson.
The trial judge now carries the responsibility for setting the minimum term for juvenile murderers.