The first thing to do is to find out exactly what the marijuana laws are in your state. Similar to prohibiting cigarette smoking and vaping, you can also restrict tenants from smoking marijuana by including those restrictions in the original lease. If you do allow smoking, you may want to include information in the lease about designated smoking areas, so that the smoke doesn't bother other tenants. Before you make any decisions, you may also want to contact your insurance company to see what types of smoking-related damage they might cover.