At the bottom of the Nav Canada NOTAM query page is a box with red text that I’ve been curious about for as long as I can remember:

Note: Under certain conditions being familiar with this section only, before commencing a flight, doesn’t meet CAR 602.71 and AIM-RAC 3.3 requirements. Please review all NOTAM files above for complete information.

I have read through 602.71 and RAC3.3. They offer no clues as to what the “certain conditions” might be, so I’ve always just ignored that phraseology and pulled all the applicable NOTAM files, slowly picking and choosing my way between stuff I care about and stuff I don’t. But I remain curious about that language: this is aviation. Nothing is a part of any process Just Because. There had to be a reason.

The answer, it turns out, is available right here. And it’s my own damn fault for not reading the manual in the first place, because the explanation is actually quite obvious when you stop and think about it. The fact that I had never actually encountered the described phenomenon is a function more of luck, or circumstance.

Interesting, eh?