Well, this has certainly opened up a can of worms.  Is pot better or worse than alcohol?  A neighbour drinking in his backyard isn't bothering me, if that's all he's doing, but pot smoke is really objectionable.  I can see that this is a situation where bylaws might be useful to make life more civil for everyone.  Just because something is not criminal, like keeping junked cars on your lawn or playing loud music late at night, doesn't mean that it's uncivil, and that's where bylaws generally step in.  If you want to live someplace where you don't have to consider the feelings of your neighbours, you need to live somewhere very far from other people.