Where There's (Pot) Smoke There's Fire

Dear Apartment Guru,

I am a building manager who is running into some issues with a few of my tenants. It would seem that a few of them are smoking marijuana. Then there is my one tenant who calls me regularly to tell on them.

The tattletale is a new tenant. Everyone else has lived there for a while. They are all good tenants in every other way and I feel lucky to have them. But I know that what they are doing is illegal. So what should I do? I don't want to get any of them in trouble with the cops. It doesn't feel right to knock on their doors and ask them to be more discrete in their smoking habits. So what do I do?

To be honest, I wish I'd never rented to the tattle-tale at all!

-- Middleman