What kind of country gets a politician rather than a doctor to prescribe medicine for a sick child? When the home secretary, Sajid Javid, decided at the weekend to allow 12-year-old Billy Caldwell “one bottle” of cannabis oil, his spokeswoman said it was an exceptional case to meet “a short-term emergency”. The only emergency was to the home secretary’s reputation. Britain is like a banana republic, in which politicians, not judges, decide who goes to jail.

It took a week of media and political pressure before Home Office officials apparently let Javid overrule them. Even then Caldwell was allowed just three weeks’ supply, “not to be taken home”, and the rest of his medicine was impounded. Javid in effect prescribed the boy’s epileptic seizures to recommence thereafter, while the remaining doses are locked in a Home Office safe. Will that constitute another “short-term emergency”?

This is inhuman and absurd. The reason for Caldwell’s treatment has nothing to do with cannabis and everything to do with ministerial terror of seeming “soft on drugs”. This terror is now archaic. Public opinion has moved on. So-called recreational cannabis is as freely available on Britain’s streets as cigarettes and alcohol. It is available in schools and universities, clubs and festivals. Most British police forces turn a blind eye to modest possession.

Why club-goers are allowed cannabis but not Caldwell is because his drug is refined, safe and requires chemical preparation. His doctor was specifically banned from prescribing the THC version he needs. Britain’s only cannabis derivatives are hard to get and not suitable for his condition.

Britain has a good record in many areas of public health. But its approach to cannabinoids is still cursed by the 1971 Misuse of Drugs Act and is half a century out of date. Patients are forced to go abroad, left with no choice, just like women from Northern Ireland who need an abortion. Home Office officials plead that they are only doing what ministers want. As with the “hostile environment” for Windrush migrants, this is hard to believe. But the remedy is with ministers. If Javid can overrule his officials for one bottle of medicine, he can do it for 10 bottles. There is no evidence from polls or public opinion that this would prove unpopular. And if it did, so what? Politicians need not surrender membership of the human race when entering the Home Office.

Theresa May, both as home secretary and since then, has condemned Britain to almost a decade of dark ages on drugs reform, while countries across Europe and America have been entering the 21st century. It’s said she could not bear to hear the word cannabis spoken in her presence. But she is weak, and Javid claims to be a new broom. He can instigate a thorough review of Britain’s drug laws, starting with cannabinoids. And he can sign Caldwell another prescription.

• Simon Jenkins is a Guardian columnist