Legal Question in Landlord & Tenant Law in California

It depends on where the house is located. In most of California, your first step is to give them a 60-day notice of termination of tenancy. If they fail to move out by the end of the 60-days, you file an unlawful detainer case just like if they failed to pay rent, only the grounds are termination of tenancy rather than failure to pay rent. If it gets that far, be sure not to accept rent for even one day beyond the 60 days or you will reset everything and have to give them a new 60-day notice. In some cities, however, there are "just cause" eviction laws on the books that prohibit evictions except with "just cause." You would have to review the applicable ordinance to see what is "just cause" in any particular city. Also, if mere use of illegal drugs (not distribution) is "just cause" you need to make sure you have evidence that is admissible in a court of law if you want to rely on that basis. Also, you should be aware that mere use and possession for personal use of illegal drugs is rarely grounds for eviction under just cause ordinances unless it is prohibited in a written lease. In most ordinances distribution or possession for distribution is required. So essentially you can't evict until there is an arrest for dealing.