Proposition 215 legalized medicinal marijuana use in California. This presents a new issue for many Property Owners and Landlords when it comes to regulating marijuana smoking in multi-unit dwellings.
Medicinal marijuana users are legally allowed to smoke inside their private residence. The new law raises questions, however, of the Landlord's duty to respond to tenants who complain about drifting marijuana smoke and what responsibilities the Landlord has to prevent the pot smells from entering a tenant’s unit.
A Landlord has a duty to maintain the premises in a reasonable safe condition. There is also an implied warranty within every lease that the Landlord will refrain from any action, and/or omission, that interferes with the tenant's quiet use and enjoyment of the premises.
It is widely known that secondhand tobacco smoke is dangerous and can cause serious health risks. So much so, California has listed secondhand smoke as a toxic air contaminant  and many CA ordinances have limited outdoor tobacco smoking within local cities . A Landlord could be found in breach of their duty to maintain safe conditions if they fail to limit the use of smoking tobacco in common areas of a multi-unit dwelling. See Birke v. Oakwood Worldwide, 169 Cal. App. 4th 1540, 1552-1553 (Cal. App. 2d Dist. 2009). The Landlord’s failure to limit secondhand tobacco smoke could also give rise to a tenant’s claim for nuisance. California Civil Code §3479 defines a nuisance as "[a]nything which is injurious to health, including, but not limited to… [that which is] indecent or offensive to the senses, or an obstruction to the free use of property, so as to interfere with the comfortable enjoyment of life or property…
So what does this mean for a tenant who suffers injury or discomfort from drifting marijuana smoke? With the legalization of marijuana use, more studies have been done on the effects of secondhand pot smoke. At least one study suggests that secondhand marijuana smoke is just as harmful as tobacco smoke.  This would suggest that the Landlord also has the duty to prevent a tenant’s exposure to secondhand marijuana smoke.
If drifting secondhand marijuana smoke interferes with the tenant’s enjoyment of the premises and/or creates health concerns, a Landlord may also be subject to liability if they merely “blow off” the tenant’s complaints about the smoke. A Landlord risks huge liability for allowing a nuisance – in this case marijuana smoke – to remain on the premises. Of course, to bring a nuisance claim, the tenant must show that there is “a…substantial and unreasonable interference, either with a public right or with the enjoyment of a [their unit]." Coppola v. Smith, 935 F. Supp. 2d 993, 1018 (E.D. Cal. 2013). In a private nuisance action, the tenant must prove an injury specifically referable to the use and enjoyment of his or her land. Koll—Irvine Center Property Owners Assn. v. County of Orange, 24 Cal. App. 4th 1036, 1041, 29 Cal. Rptr. 2d 664 (1994).
But what are the Landlord’s responsibilities to the smoking tenant? The Landlord may be concerned that limiting a tenant’s lawful right to medicinal marijuana could also give rise to liability to the smoking tenant for discrimination. However, medicinal marijuana users are not protected under the American Disability Act (“ADA”) because marijuana is still considered an illegal drug.
To avoid these issues, Landlords should consider making their properties “smoke free.” If they choose not to declare the property a "smoke free" zone, a tenant’s concerns about drifting marijuana smoke should not be ignored as there may be some serious implications for the Landlord.
 California Identifies Secondhand Smoke as a "Toxic Air Contaminant"http://www.arb.ca.gov/newsrel/nr012606.htm
 Smokefree Outdoor Air http://www.no-smoke.org/learnmore.php?id=669
 Secondhand marijuana smoke may damage blood vessels as much as tobacco smokehttps://tobacco.ucsf.edu/secondhand-marijuana-smoke-may-damage-blood-vessels-much-tobacco-smoke
 Medical Marijuana Use Not Protected by ADA http://www.workforce.com/articles/medical-marijuana-use-not-protected-by-ada-appeals-court