Does a Pill Jag Count As a Slip?

I know a person who is planning to celebrate three years of "sobriety." He hasn't had a drink in three years. He has been a sturdy member of A.A., often a speaker. For the past eight months, however, he has been using pills secretly. On a number of occasions, he has appeared at meetings and elsewhere under the influence of these drugs. Has he had a "slip?" Can he honestly celebrate three years of "sobriety?"