Even by the standards of modern legislation, the psychoactive substances bill is startlingly inane. It seems to ban any substance which can cause a mental or emotional reaction. As must be obvious, that's almost everything in the world. Did this taste remind you of your mother's cooking? It's a psychoactive substance. Did it bring you a moment of happiness? It's a psychoactive substance. The government is about to ban almost everything.

This is not, to be fair, the legislation. This is just the advert. But the description of the bill in the Queen's Speech is troubling enough.

"The Bill would make it an offence to produce, supply, offer to supply, possess with intent to supply, import or export psychoactive substances; that is, any substance intended for human consumption that is capable of producing a psychoactive effect. The maximum sentence would be seven years’ imprisonment."

Note the line "any substance intended for human consumption that is capable of producing a psychoactive effect".

That therefore includes all substances, given that at the point someone was caught by police it would only be pertinent if they intended to give it to other people.

The World Health Organisation defines psychoactive as:

"Psychoactive substances are substances that, when taken in or administered into one's system, affect mental processes, e.g. cognition or affect."

So at this stage everything is included.

There are, of course, rather substantial caveats. The next section says:

"Substances, such as alcohol, tobacco, caffeine, food and medical products, would be excluded from the scope of the offence, as would controlled drugs, which would continue to be regulated by the Misuse of Drugs Act 1971."

So existing illegal drugs are exempt. So are existing mind-altering drugs which are legal, such as alcohol. Food is exempt, which gets rid of our 'mum's food' example above. And so is caffeine, although it seems that whoever wrote it did not know that theobromine has a stimulant effect on the brain and is found in tea and chocolate. Chocolate will be OK because of the exemption on food, but hot chocolate won't. So that might need fixing before they end up criminalising half the country.

You'll notice as well that solvents aren't mentioned. The food exemption also raises the question of what you do about people who cook legal-high versions of cannabis into cakes or biscuits. Professor David Nutt's plans for a safer version of alcohol, which could save millions of lives, would be illegal right off the bat. In fact, it's worth considering for a moment how far-reaching these plans are. The world is now illegal until proven otherwise.

That seems to stretch what might be considered the valid powers of the state into the world of fiction. 

How has it happened that such a nonsensical idea could find its way into a Queen's Speech? The story starts in New Zealand. When they experimented with a different approach, world governments realised that being sensible about legal highs meant bringing the war on drugs to its knees.

This is their problem: Once a new legal high is blacklisted, those clever chemists alter its composition just enough that a new one does not fall under the remit of the law and can be freely sold. Chemists – especially those with the appropriate financial incentive – typically work faster than legislators.

New Zealand had a particular problem with this. It's out in the middle of nowhere and there aren't many people living there. Drug smugglers weren't really keen on finding routes into the country. But demand still existed, because Kiwis are humans and if you give humans the opportunity they will take drugs.

So legal highs were very popular in New Zealand. The government came to a sensible solution. It would offer drug designers the chance to get approval for their products if they could convince a Psychoactive Substances Regulatory Authority they were safe. It was a great idea and passed with just one vote against. And then it all went wrong.

Because the world is sillier than any of us are really prepared to admit, it went wrong not because of a backlash by drug prohibitionists, but because of animal rights activists. The interim licensing sections were repealed and a section added banning the advisory committee from authorising a product where the trial for its use involved the use of an animal.

Putting aside the eccentricities of Kiwi politics for a moment, the reasonable original proposal was profoundly dangerous for supporters of the war on drugs. It threatened the idea that drugs must be banned, regardless of harm, out of some quasi-religious anti-intoxification agenda. It introduced the notion that drug regulation should take place on the basis of evidence of harm, rather than some sort of historic crusade. Basically, it was sensible. And because it was sensible, it was a threat to the global system of drug regulation.

So if you can't do that – for fear of undermining half a century of madness – you have to go the other way and ban everything until its proved it won't do anything in your head. That is the oh-so-sober suggestion of the drug warriors: they want to ban things which make the brain do things. It's basically a war on subjectivity. A child would know it was madness. Only a civil servant could think it was sound policy.

It's easy to laugh, but what has happened here is a dark legal turning point in British history. Previously, everything was legal unless the government passed legislation outlawing it. That is the benefit of not having a constitution – your freedoms are not granted, they are only ever taken. It makes legislation a sober undertaking which demands responsibility and sincerity from those who write and vote on it. It is the great achievement of British society: the idea that the people are free and the government must justify its intrusions, not the other way round.

This is the opposite. It is the spilling of the legislative ink, so that it covers everything. It is the rank opportunism of the state at its worst. And it is contrary to the legal basis upon which this country has operated for hundreds of years.