“I am a landlord. Can I request that my building be cannabis free?”
In general, you would be able to request that cannabis use not occur within your building. However, as a landlord you may not be able to enforce this across all or possibly any consumption method, depending upon the situation.
Individuals are not prohibited from consuming cannabis within their private dwelling, according to the Cannabis Control Act of NB. Though there are other places where consumption of cannabis is not legal, a private dwelling is not one of them.
Smoking & vaping of cannabis falls under the same rules in New Brunswick as smoking/vaping of tobacco. The Smoke Free Places Act details what places are prohibited for these actions in NB. Within the list of prohibited locations you will notice any "enclosed public place" - this includes the common areas of multiunit residential buildings. However, within this Act you will also see that a "private residence" is a location where smoking/vaping is explicitly permitted.
It would appear as though in New Brunswick a tenant is generally allowed to consume cannabis legally within their own private residence. Unless a lease, signed by tenant and landlord, says specifically that smoking is prohibited then the tenant would have the right to smoke/vape within their rental unit. Common areas of a multiunit residential building, on the other hand, are locations where consumption is clearly not allowed.
For any details that might need further interpretation based on your specific situation, please feel free to reference the following:
Cannabis Act (Canada)
Cannabis Control Act (NB)