A 15-year-old boy has won a landmark High Court challenge to the legality of child curfew zones used to tackle anti-social behaviour.
The teenager said the use of dispersal zones in Richmond, south-west London, breached his rights under the European Convention on Human Rights.
Unaccompanied under-16s found in zones after 9pm can be held and escorted home, whether badly behaved or not.
The Home Office said it would be appealing against the ruling.
The police and Richmond Council had argued that curfew zones reduced anti-social behaviour.
The High Court ruled that the law did not give the police a power of arrest, and officers could not force someone to come with them.
Lord Justice Brooke said: "... All of us have the right to walk the streets without interference from police constables or CSOs unless they possess common law or statutory powers to stop us.
"If Parliament considered that such a power was needed, it should have said so, and identified the circumstances in which it intended the power to be exercised."
In a statement after the ruling the boy, known in the case as "W" and described as a "model student", said: "Of course I have no problem with being stopped by the police if I've done something wrong.
"But they shouldn't be allowed to treat me like a criminal just because I'm under 16.
"I am very happy with the outcome it is a good victory. I'm glad that the police can't just use force against us anymore.
"I am happy that I won't get into trouble with the police just for being young."
BBC Home Affairs correspondent Rory McLean said the test case ruling had major implications for the government's anti-social behaviour policy and may require legislation in order to deal with the issue.
A Home Office spokeswoman said dispersal zones already in place and future applications were unaffected by the judgment.
"These powers provide the police with a powerful tool to tackle intimidation and anti-social behaviour by groups of people," she said.
"Whilst not limited to young people, 'teenagers hanging around' is a big cause of concern to the public as cited in the British Crime Survey."
During the case heard in May, Javan Herberg, appearing for the teenager, said the curfew zones violated the human rights of "wholly innocent" young people.
He told the court that more than 400 zones had been introduced under the 2003 Anti-Social Behaviour Act. While this case involved Richmond, its implications could be much wider, he said.
The Home Office, backed by lawyers for the police and council, argued the application for judicial review should be dismissed and said the zones did not breach human rights or common law.
They said the 15-year-old could not bring the claim because he had never been stopped by police inside a dispersal area.
The boy was backed by civil rights group Liberty.
Alex Gask, Liberty's legal Officer acting for "W", said: "This is a victory for the presumption of innocence, and the right of everyone, no matter what their age, not to be subjected to coercive powers without good cause".