The issue is whether the disclosure of the information in question will be harmful to the interest protected by the exception. When we say that something is likely injurious, we are distinguishing it from something that is potentially injurious, something that is feared to be injurious. It has to be more than something that is vaguely apprehended to be injurious. There must be facts involved.
In practice, this means that when there is a challenge about the enforcement of an exemption or a test as to what is injurious, we have to present evidence to the court to convince the judge, who will judge not only the law but also the facts and will decide whether we have done what was required of us.
In access to information cases, I must confess that this is a problem, for those of us who work in the field, when the government manages to prove that something is likely to be injurious. To do this, the government often uses information that is confidential and that would be injurious to disclose. This information is disclosed to the court in confidence. The court has full access to the information, and in its judgment, which is public, if the court agrees with the government, will not reveal the exact nature of the evidence to the extent that this would disclose the confidential information.