Um.
Cannabis is as legal for minors as it ever was. So how can you blame the law?
The argument is that it is probably easier for minors to get it now that it's legal for adults.
Just like kids getting liquor from a liquor store years ago.
KID: Hey dopehead, I’ll give you 40 bucks to buy some dope, and another 40 to buy some for me, DEAL?
DOPER: UUHHH, sure DUDE, why not.
Or just steal it from doper mom and dad, after all when they are stoned they won’t really remember how much they had left.