The Supreme Court heard the case of a young person whose career was blighted by the threatened disclosure of two youth reprimands, imposed when he was a young teenager.
Such disclosures on Disclosure and Barring Service (DBS) forms are "directly inconsistent" with their intended purpose as a diversion from the criminal justice system and is a breach of the right to privacy, the judges found.
Charities involved in the case have now called for the government to conduct a review of the disclosure regime for children and young people.
The young man in question was aged 13 when he received a police reprimand, in September 2006.
In 2011, he lost his job as a library assistant after enhanced DBS checks were required, which would have flagged the reprimand. Since then, he has felt unable to apply for jobs where enhanced checks are needed.
Children's charity Just for Kids Law argued that the policy fails to treat children differently to adults and contravenes Article 8 of the European Convention of Human Rights.
Such disclosure is "disproportionate and unnecessary", said the charity. This is because reprimands and final warnings - which have been replaced with youth cautions - should be primarily a rehabilitative measure, and not a punishment for life.
Under current law, reprimands appear on standard and enhanced DBS checks until the holder is 100 years old. A basic police check will not flag most cautions and warnings because a vast majority are spent.
Experts estimate that more than a million youth criminal records relating to offences more than 30 years old were disclosed by this means in the last five years.
Enver Solomon, the charity's chief executive officer, said: "We are delighted that the Supreme Court has upheld the decision of the Court of Appeal in favour of our client and are proud to have secured a landmark judgment that will benefit thousands of children issued with cautions each year, a shockingly disproportionate number of whom are from black and minority ethnic backgrounds.
"Our client should never have been given a criminal record that stays with him for life.
"This judgment makes clear that the disclosure of reprimands and cautions, the legal equivalent of a slap on the wrist, is disproportionate and damaging to the future rehabilitation of children, preventing them from moving on from their past.
"A parliamentary inquiry reached the same conclusion nearly two years ago when it stated that children were being unfairly denied a second chance.
"There is now an overwhelming view shared by the higher courts and MPs that the government should act immediately to ensure no child who is given a caution ends up with a criminal record that stigmatises them for life.
"The government should also now conduct a wide-ranging review of the entire criminal records disclosure regime for children and young people."
Christopher Stacey, co-director of charity Unlock, said that criminal checks leave many people "unnecessarily anchored to their past".
Stacey said that recent reviews by the Law Commission, Justice Select Committee, Charlie Taylor and David Lammy MP, have all suggested an overhaul is needed, and called for the government to act.
This judgment is the latest in a number of landmark rulings secured by the Just for Kids Law strategic litigation team, whose work has previously led to changes in the law on joint enterprise, the holding of children in police cells, and the eligibility of young migrants for student finance.
