I will try to give an example, and it's an old example already. Let's say a professor is looking to present a class on the presentation of professors in popular culture or the presentation of politicians in popular culture, and they want to show some clips from a DVD or a video, or some kind of streaming mechanism. It may be that they have to break into that in order to copy those clips. Let's say it's a two-hour movie and they want to show two minutes of it. It may not even reach the threshold of fair dealing. It may be an insubstantial use, so it's perfectly legal to do that in terms of what the Copyright Act says, but because you're not allowed to break digital locks, it would be an infringing activity.
Evidence of meeting #101 for Industry, Science and Technology in the 42nd Parliament, 1st session. (The original version is on Parliament’s site, as are the minutes.) The winning word was access.
A video is available from Parliament.