I always assumed that the expiration date was partly legal, in the way that you only have 1 year within which you can legally have the drug in your system.
Are you implying that you still hold this assumption and are looking for someone to convince you otherwise? If so, I can't even conceive of where you got this idea in the first place, let alone argue against it. Let's slap a little Occam's Razor on this: how would you even begin to enforce this?
According to my research, in America it's mostly an unknown (unenforced or depends on the state's sometimes conflicting verdicts) whether having a drug in your system means you are in possession of said drug. There are other laws that relate but I cannot pretend to understand the intricacies of which laws might apply to this situation.
But yes, I am interested in a definitive answer.
Laws around prescription pills are sometimes unexpected, like every prescription pill in your Mon-Tues-Wed-etc pill box (outside their prescription container) being a felony. So my grandma has numerous unexpected felonies in her purse.
Are you implying that you still hold this assumption and are looking for someone to convince you otherwise? If so, I can't even conceive of where you got this idea in the first place, let alone argue against it. Let's slap a little Occam's Razor on this: how would you even begin to enforce this?