If the tenants are renters you might be able to inform the owner on the chance they are unaware what is going on, (and even just letting them know that their name is being mentioned as much). Unsure there, but as I understand it, in Qld if drugs or anything illegal is/are busted by police on the property the owner also gets pinged. I advised an agent of that (right or wrong? – dont care) and the problem tenant was gone that afternoon.