Section 312 — Criminal Code: Publication invited or necessary

No person shall be deemed to publish a defamatory libel by reason only that he publishes defamatory matter on the invitation or challenge of the person in respect of whom it is published, or that it is necessary to publish in order to refute defamatory matter published in respect of him by another person, if he believes that the defamatory matter is true and it is relevant to the invitation, challenge or necessary refutation, as the case may be, and does not in any respect exceed what is reasonably sufficient in the circumstances.