It depends is it an addiction or just a fun thing to do occasionally that he can move on from easily? Without losing friends, pleasurable habits that have been integrated into his life, and also withdrawals from the drug itself?
To be honest, I know people who are addicted / have had long term relationships with guys whose first love is dope, and it’s not fun.
Basically, you have to be into that scene to be around them, as unless you’re into smoking cannabis as well, you notice and have to acccept so many negative behaviors... and as a consequence it does rip couples apart.
The specific problem with cannabis is that culturally it’s kind of accepted compared to other substances that cause addictions (like other drugs for example), and antisocial behaviour / ruining someone’s life etc... so unfortunately you can often look like you’re the uptight person with the problem if you object to your partner having an addiction to cannabis.
I should say that addiction is so much different to just smoking it socially and enjoying the effects.
Addiction means dealing with dope in your life on a daily basis and dealing with such negative consequences like, well, impotence, for example, lethargy, lack of concentration, short term memory issues, paranoia, depression etc etc etc... and from a partners perspective, simply never being able to sit for a whole evening and just enjoy it because the other person in the room is yearning to go outside and be with his first love which is unfortunately not you.
I wouldn’t even try and make it work under those circumstances. It just leads to pain.
Nowadays having seen what these relationships have done to my friends I would stay well clear, however 10 years ago I would have jumped into a relationship happily thinking that everything would be OK and that I was a stick in the mud to be worried about anything I guess it really depends on your experiences!