Many students are more or less worried than they should be when dealing with Public Safety. They are not here to prosecute students—they are here to ensure student safety. If there is a dangerous situation, Public Safety is there to sort it out and not to throw punishments around.
When someone gets caught on minor drug violations, a warning or “housing probation” is often issued. This basically means that a student cannot be caught again during the probationary period, or they will lose their housing. This second part is usually not enforced unless someone is dealing. If you mind your own business, are considerate, and are not too obvious, you should be fine.