Britain's High Court has ruled that children under 16 considering gender reassignment are unlikely to understand the risks of the drugs they are taking.
It says the experimental nature of the medicines that delay puberty mean the courts should decide over the administration of them - even for adults.
Hormone blockers are drugs that can pause the development of puberty and are sometimes prescribed to help children with gender dysphoria by giving them more time to consider their options.
The case was brought by two claimants against a National Health Service trust that runs the UK’s main gender identity development service for children.
One of the claimants, who was prescribed hormone blockers at 16, argued that the clinic should have challenged her more over her decision to transition to a male.
Tuesday’s ruling will “protect vulnerable young people”, said Keira Bell, who is now 23 and has stopped taking cross-sex hormones. She added that she was “delighted to see that common sense has prevailed”.
However, Susie Green, who is the head of Mermaids, a children's trans charity, disagrees and says the court's ruling is disturbing.
Green says puberty blockers have been used for decades to treat gender dysphoria and the effects are entirely reversible. She added that fewer than 1% of people who use these drugs regret their decision.
"So what this judgment is doing is ruling for that one person who may change their mind. The 99 others must go through a puberty that doesn't align with who they are. Frankly, that's torture."