(And I know twf protested this earlier in the thread, but in my experience the Venn Diagram of marijuana users and those who push for its legalization very nearly forms a single perfect circle. With that in mind, the answer to your question is going to be…probably not.

)
Not quite so fast. I’m not a user, but I am skeptical about the societal value of criminalizing marijuana cultivation, sale, and use. There is such a thing as a cure that is worse than the disorder it aims to address.
In spite of the number of people who had no legitimate need who still managed to find some quack willing to write a script for their “medical” marijuana card, I do know cancer sufferers and others who actually did use marijuana medicinally and responsibly. From a strictly rational standpoint, the concerns posed by marijuana’s pharmaceutical properties, while different from those of alcohol, are not universally worse than alcohol. In spite of my recognition that alcohol can be used moderately and without the intention of achieving impairment, I also recognize that impairment is a very common goal of alcohol use. I don’t see any pharmaceutical reason why the two substances belong in separate classes. From the standpoint of the police, for instance, saying that adults
can use alcohol without being too impaired to think straight is splitting hairs, since so many use it precisely in order to get drunk.
There was once a hysterical opposition to alcohol which unrealistically thought Prohibition could stop the evils that come from immoral use of alcohol. From that example, it is quite clear that we can be both right-minded and wrong-headed about how the law can most effectively deal with the societal hazards posed by mind-altering substances.
**But…back to the OP. **To make someone your boyfriend isn’t just a form of especially approving of him as a friend. It is not the same as marriage, but it is a position of trust. No matter what the OP or anyone else might think about the legalities of this behavior or that, she must always remember that she and she alone has the authority to decide which behaviors she will or will not tolerate in the person she puts into the position of trust and mutual concern that a boyfriend is to her.
No argument should be allowed to persuade her that she must tolerate a behavior that makes her stomach churn. She has the authority to decide she won’t. To exercise that authority is not judgmental, it is not unforgiving, it is not unfair. No one is entitled to that position of trust with her.
If anything, it is unfair to put someone into a position of trust that he is inherently incapable of filling without betraying that trust.
She must understand that she does not have the power to control another person. She will do well to choose to trust a fellow who is constitutionally inclined to live according to the boundaries that also suit her. In that case, she will have a partner she can trust, rather than one she has to police. She is too young to be anyone’s warden, but no one who is realistic tries to make another human being into a “fixer upper.” Al-Anon’s mantra is “I didn’t cause it, I can’t cure it, and I can’t control it.” Avoiding the temptation to control another human being or to covertly compensate for serious and habitual faults is very important to anyone who wants a healthy marriage, that is for certain.
OP, look soberly at whether this young man is constitutionally inclined to be the man you need him to be. If not, be realistic and let him go to find a better fit for himself. You keep looking until you find someone who will be what you need merely by being himself.