what you're really after is not the banning of smoking of it (or smoking anything else at all, like tobacco), but the smoking of it specifically in public places ... and smoking in public places is already a commonplace ban ... you can basically come closer to forcing the smoking into people's own homes and keeping it out of everyone else's nostrils
you'll never be able to ENFORCE an outright ban, on pratically anything short of private ownership of nuclear weapons (I'm not even sure how perfectly gun bans work in countries that have them, even though I'd support a gun ban in the US ... except when you need to shoot the MAGA ICE agent who wants to shoot you for no effing reason, maybe us libs do actually need guns, I dunno)
I'd be more interested in regulating where pot can be sourced, like this is a plant originating in central Asia, it makes zero sense to grow it anywhere in the US (it sure AF doesn't make any sense to grow in NorCal redwood forests), it is a thirsty non-native species that is bad for the environment in North America, and it is epically stupid to grow it indoors with a high electrical / carbon footprint just for the sake of legalizing it (see states like Washington which take this route) ... this is a plant that needs to be grown outdoors in a climate with nots of rain where it is not displacing native species or drawing away groundwater from native species ... so basically force people in the US to buy pot imported from Asia, and require it to be certified that Asian pot plantations didn't have to clear e.g. orangutan habitat in order to exist, and dismantle the domestic commercial grow ops that have sprouted up in states where it's been legalized
I mean pot can very much be legal to consume in the US, but it can also be treated very much as the highly non-essential plant that it is (e.g., it ain't food, it ain't needed for survival, and bubble burst, UCSF research is showing that it does indeed have negative health effects, regardless of the method of ingesting it), so it doesn't even have to be affordable to be legal
to actually make Earth pristine and cleanse it of all negative human behaviors (e.g., litering is already illegal, but you'll always see cigarette butts out in the environment, because smokers are often shitty entitled people who think their litter is a magic exception, and even movies and tv continue to normalize smoking and tossing butts onto the ground), you'll need to find a way to make the entire human species completely extinct, forever, as far too many negative entitlements are completely normalized at a collective level
