night vision
All generations are legal to own in Canada, the issue as has been noted is getting anything beyond Gen 1. There are Eastern European made units that work just fine available, but cost tends to be the issue. With a Gen 2 scopes running 2500 +.
I did some quick checking a gen 3 and 4 stuff seems to have dried up, so there may be something going on there.
You can not get anything out of the US, nor can you send anything to the US for repair.
Depending on your needs a good gen 1 Scope, with an IR illumination works fine. I use a Pentagon flashlight light and USNV product IR filter. Thermal imaging scopes are an amusing price starting at 10K and going up.