The fact is, this doesn't actually change anything. All this proposal does is encourage Country A to employ sanctions when Country B doesn't stop people from bringing drugs that are outlawed across their shared borders. Country A already has that option, so it doesn't need to be encouraged; nations do this sort of thing all the time.
If drug Q is illegal in Country A, Country B should stop them; not passing this proposal does not make the traffickers' actions any less illegal. If something already against the law, why should we force nations to pass new laws making it extra illegal?
If drug Q is legal in Country A, Country B does not have to stop anyone carrying it; this doesn't make transporting legal drugs suddenly illegal.
I simply don't see the point in needlessly complicating things.