Plagiarism and moral rights
Plagiarism occurs when an author uses another’s work without acknowledgement. Plagiarism is an issue of academic integrity separate from any question of copyright infringement.
However, under the Copyright Act, authors have the right to have their work properly acknowledged when it is quoted, and the right not to have their work subjected to unreasonable derogatory treatment. These rights are called "moral rights" and are separate from copyright. It is an added reason why it is important to acknowledge the sources you use. For more information on moral rights, consult the guideline Copyright Guidelines for Moral Rights (PDF, 34KB).