How can this be? How does this happen? You get a call? You are mailed a letter? An "authority" asks you if you know so_and_so? You say, yes, I know that person. They say is he/she such and such, have they done such and such? How can they make you tell them everything?
For instance, you might have smelled pot when you walked by their bedroom. You might have even seen a bong or hash pipe that you figured belonged to them. If they ask if that person partakes of pot you can honestly say you don't know. Having a pipe doesn't guarantee they use it. Smelling (or thinking you are smelling) pot when you pass their room isn't proof they are a user. Maybe it was someone else, smoke that was blowing in their window, or possibly there was someone else in their room using. Even if you saw them smoking something how can you be sure it was pot? See what I mean. You can refuse to answer in the affirmative (if you so choose), without lying, if you don't have incontrovertible evidence. How then can they prove you were lying. Some things are more clear cut, of course, like did they live with you.