After a quick search I can see no threads that debate this issue in specific, and it doesn’t seem to be part of the larger legalization debate, so let’s do it:
Regardless of whether it’s legal, secondhand marijuana smoke is harmful.
To begin with, it’s smoke, which necessarily irritates the lungs and eyes and causes damage after nontrivial exposure.
Secondly, and more dangerously, it’s intoxicating smoke, which means you can’t easily evade it, and it alters your cognition without your consent. I think the experience with non-smoking sections in restaurants and, earlier, airline flights amply demonstrates the standard fluid dynamics idea that any gas will expand to fill any volume it is placed in, and just as secondhand tobacco smoke has a nontrivial nicotine content, secondhand marijuana smoke must have a nontrivial THC content.
I honestly do not think the facts laid out in either of those above paragraphs are in dispute, and it worries me that they’re simply being ignored, instead.
So what is my solution? Greatly restrict the areas where people can smoke marijuana: No marijuana smoking outside, in businesses that don’t explicitly cater to the marijuana smoking trade, or in moving vehicles. That last would entail a ‘lit joint’ or ‘lit bong’ law stricter than modern ‘open container’ laws, and, given the area effect of the THC haze, such a law would have a much greater justification.
My idea of ‘businesses that explicitly cater to the marijuana smoking trade’ is essentially the notion of tea houses and marijuana clinics: Places where the only reason someone would go in would be to smoke marijuana, so inhaling secondhand smoke in addition to their own smoke would not be an important aspect of the experience.
As for enforcement, recklessly making non-smokers smoke, especially something mind-altering, is either assault or, at the very least, reckless endangerment. This includes scenarios where apartment dwellers force their THC haze on people who live in the same building or home dwellers force their haze on people who live on the same block (although it is difficult for me to imagine anyone who gets so fried you can detect it from the next house).
Is anyone seriously opposed to these ideas?