Along the same lines:
> 1. Spike the drug supply with a slow acting poison. Lots of poisons to choose from to make this work.
No there aren't. Drugs are super strong, concentrated, and great at being drugs. They have varied and various manners of consumption, and can be purified on-site of many adulterants. You'd be looking at a bevvy of poisons, each one easily thwarted. Fentanyl or something of its ilk is a better solution. Those drugs are also used in niche communities with connections to their distributors, they would notice people dying.
This is before we look at at the giant, unending, economic incentives for criminal cartels to avoid this poisoning.
> 2. Conduct continuous drug testing of the entire population (say once a week) with harsh penalties for failing.
Sounds awesome, wanna know why it won't work? Even if the absurd costs of administration & enforcement could be handled, we do not have the money for testing at that level. More importantly the metabolic processing rates for drugs are very different. Cocaine, for example, is only 3 days. Storage of materials required for post-facto processing is also a huge cost. And even if any of this were viable we have the issue of sister chemicals and the ongoing testing war with cheap chinese chemical producers, an arms race we are losing and would lose harder and faster.
To be concrete: random USADA testing of two athletes ranges in costs from $50,000 to $100,000 for 7 to 8 weeks. Even that is highly circumvent-able if you were only looking for short-acting drugs.
> 3. Apply a mandatory death penalty for any drug use (especially if combined with 2).
Cruelty always makes social change easier, but let's look at any historical example where this has been tried... ... did it stop drug use? No.
Not to mention how nice it would be to put some THC oil into the food of my enemies and then have them executed by the state...
Not to mention the GDP costs...
Not to mention that in the real world the death penalty costs more money than lifetime imprisonments...
> 4. Immunise the population to induce anaphylaxis if drugs are consumed (this one is technically possible, but it would need further research).
That's not really how drugs work, that's not really cogent of how designer drug development works, and whenever I hear suggestions requiring man-hours enough to build the pyramids by hand... well... I think they're about as likely as us building all the pyramids over again by hand.
Aaaand again I find the idea of being able to murder people from easily attainable substances and well understood chemical compounds that can be readily be put into foods or aerosols kinda fun, and definitely something that would work out well in practice...
Naturally, the impacts on GDP would make this about as likely as Trump making real estate illegal.