Well, I will surmise that you have completed your O/W training and are now a certified diver.
If this is the case, then it would probably be prudent if you were not to be associated with the instructor in question. The reason ??? Guilt by association.
If you are still working on your O/W, stop the instruction, obtain a referral and continue your course with another instructor.
If you are ABSOLUTELY POSITIVE, BEYOND ANY REASONABLE DOUBT that the instructor was using a controlled substance, then report the instructor to the PADI Quality Control division. Keep in mind, you open youself up to litigation if certain statements are made which cannot be substantiated and result to "damages" suffered by the accused.
the K