We can eat poppy seeds in bread, but that's a huge leap to allowing people to grow opium poppy that heroin that is extracted from and medical diamorphine is made.
The medicinal cannabis oil that is in the news has had the active compounds extracted so the oil is standardised and therefore the dose is controlled. Like all medicines it has to be tested and approved. Most drug testing is done on consenting adults, there are big ethical issues with testing on children and although children and young adults are prescribed controlled drugs its done with caution.
We have had huge problems in the past with drunk drivers, I never drink and drive, I know my reactions would be slower. The thought that there would be another substance allowed for the general public to take that alters their reaction times and behaviour on the roads fills me with dread. I have looked after people would are seriously injured through drink driving, the worst brain injured, broken bodies do heal if not perfectly, there is nothing sadder for the family than an altered person due to brain injury.
If medicinal cannabis is prescribed I am sure it will be on a name patient basis and a Controlled Drug, with the caution not to drive. If you smoke cannabis for recreational use, like cigarette smokers, don't come near me, it stinks and pervades walls an carpets, I have learnt to my cost. I rented a house and five car bombs, used in every room, vinegar bowls and two years later and you could still smell it. Ugh.