LAWS that make consensual sex between teenagers a crime are unconstitutional, a high court found on Tuesday.

The Criminal Law (Sexual Offences and Related Matters) Amendment Act has been widely condemned as absurd and unenforceable. It makes it a criminal offence for children between the ages of 12 and 16 to have sex — even when they consented to it.

It also makes consensual kissing, and even cuddling, an offence if there is an age difference of more than two years between the children.

Last year, the Teddy Bear Clinic and Rapcan challenged the act in court, arguing that instead of protecting children, the effect of the law was to traumatise them by exposing them to the criminal justice system.

They put surveys before the court that showed that up to 80% of children between 12 and 16 had kissed, up to 33.8% had engaged in heavy petting and up to 26% had had sexual intercourse.

The act also says anyone who sees teenagers of certain ages kissing must report it or be guilty of an offence.

In his judgment, Judge Pierre Rabie said it was clear that “sexual violation” was defined so broadly in the act that it “includes conduct (such as kissing and light petting) that virtually every normal adolescent participates in at some stage or another”.

“There can be no doubt that the impugned provisions, as they stand, infringe a range of constitutional rights of children,” he said.

The judgment was hailed as a victory for children’s rights by Rapcan and the Teddy Bear Clinic.

“Professionals and parents are now able to provide children with the necessary support and guidance about sexuality ... without fear of incriminating the child or themselves,” said Rapcan.

The two organisations emphasised that the judgment did not affect or deal with any acts of sexual violence. “It deals exclusively with consensual sexual acts between children,” they said.

In his judgment, Judge Rabie said to subject “intimate personal relationships to the coercive force of the criminal law” was to “insert state control into the most intimate area of adolescents’ lives”.

Any legislation that did so should be “carefully and narrowly crafted to infringe on these vital constitutional rights as little as possible”.

In this case, the act was overly and unjustifiably broad, he said.

He dismissed the arguments made by the justice minister and the national director for public prosecutions, who had defended the act.

They had argued that there would be no harmful effect if the act was read together with other laws governing children — which put children’s best interests first and tried to “divert” them out of the criminal justice system to avoid prosecution.

But Judge Rabie said: “Despite many reforms to make the child justice system more child-friendly ... exposure to the criminal justice system is still a dramatic and harrowing experience.”

He said even if prosecution was avoided, children could still be arrested, questioned by the police and detained in police cells. There was “no doubt” that this would have negative consequences.

Judge Rabie tailored his order carefully, so that it would still be a crime when the sexual conduct was between adults and children, or where it was not consensual.

The judgment must now be confirmed by the Constitutional Court.