Alcohol on the other hand mostly just knocks you out from doing anything too cerebral after you pass the ballmer peak. I say this as a person who prefers weed to alcohol 100x.
As for mental health issues worsening due to THC - that's true, but alcohol has a much higher probability of causing or exacerbating such problems. On the other hand, the therapeutic use of THC has seen much better results than alcohol. If both happen to be legal in that jurisdiction, then banning weed but not alcohol really doesn't make sense. Further, even if possession is illegal, smoking itself (without inhaling, or however that went) isn't against the law in many places.
It really just seems arbitrary and strange, unless there was a psychiatric evaluation that we're not aware of, or this happened somewhere where weed is very strictly illegal (think alcohol in Saudi Arabia-level).
That's pretty minimizing of alcohol's contribution to violent acts (bar fights, escalating disagreements at supermarkets/etc, domestic violence) as well as vehicle collisions.
Were he high on weed, maybe he'd not commit the felony in the first place. Yeah, banning him from alcohol is fine, from stimulants broadly - also OK, but weed? Honestly? How often, statistically speaking, does smoking weed make a person aggressive? While this person may be an outlier, without precise information on it, I'd say the ban on weed is as sensible as a ban on butter or relanium. If it doesn't serve any obvious purpose (like with alcohol: being drunk makes you do stupid things more often), then maybe it's really just a way of harassing this person?