What do I do when a guest breaks a house rule

[Niki229]

I have a guest who I realized broke one of my house rules— no smoking/drug use on the property. It is my only house rule so I can’t imagine it is easy to miss. I’m a woman who lives alone on the property and the thought of confronting a male guest alone frightens me. 

What at do you typically do in this situation? Just leave a bad review?