B-1, r. 3.1 - Code of Professional Conduct of Lawyers

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45. A lawyer must notify the client of any fact learned by him in the performance of his professional services which, in the lawyer’s opinion, may be a breach of the law by the client.
If the client is not a natural person, the lawyer must give such notification to the representative of the client with whom the lawyer deals when providing his professional services. If the lawyer later becomes aware that the client has not remedied the unlawful situation, he must notify the appropriate hierarchical authority.
O.C. 129-2015, s. 45.