I thought I post an update about the solution to the pot problem in my apartment building. I'm really happy with this solution, as I feel it meets the needs of my neighbor, who wants to smoke pot and not get evicted for it, and the needs of myself and other neighbors, who want to live here without being exposed to marijuana smoke on a regular basis.
The property manager of our building had the maintenance staff install some sort of heavy-duty weather stripping around the neighbor's door, in order to make it less likely for smoke from inside the apartment to drift out into the hallway when the door is closed. He also purchased an air purifier or air filter, something with a HEPA filter, for the neighbor's apartment. This is not an appliance typically provided by management, so the neighbor was asked to pay for it. However, he is being permitted to pay it off a little at a time, since he was not able to pay the full cost at once.
It seems that these steps have solved the problem, because I have not smelled pot smoke in a few weeks now.