Unfortunately, as a society, we are on the hook for supporting all those who become permanently brain damaged as a result of pot use. The evidence suggests that even a small use can cause permanent brain damage.
If we just look at cost-effectiveness, which is more costly: providing lifetime support to those who destroyed their own brains, or enforcing drug laws and keeping it illegal? I do not know this answer--it is probably worth a study or two to answer.
wait, he overdosed on pot? That can’t be true because potheads have been telling us for years that it’s unpossible.. “pfttt....dude, you can’t overda... wait wha? ohhh, riggggghhhhhttt.... you can’t take too muc..... wha?”
That establishes a premise that we will be "on the hook" for supporting them and circumvents any debate about whether we should be, and carries an implicit assertion that the perception of "risk" automatically creates a government power to act on it.
The validity of that premise needs to be challenged, IMHO.