I've been lurking for a while, and have always contemplated the American POV of this topic...
While firearms laws are obviously different, they're similar at least in the sense that we can both own them (firearms) because we don't live in Communist countries.
To hopefully shed some light on this subject, there are a number of items & firearms that us Canadians would love to purchase from you - but simply aren't allowed (Prohibited). Suppressors being the most notable.
Then there are items that our country will allow us to have, but have to go thru a "process" to allow it's entry - like magazines being pinned. All firearms coming in get checked for compliance & theft.
Everything else firearm-related (coming or going) is generally not regulated per-say, especially when it comes to used goods... Barrels, BCG's, scopes, nightvision, etc. Nothing, except incoming receivers/firearms.
Nobody has control over what I sell or to whom. It's completely up to the buyer to ensure it permissible into their country, if it gets held by their "Customs" agency - not my problem.
* I guess the only question I have is - Does ITAR, the Dept. of Commerce, or Dept. of State have any authority over (private) sales, other than a serialized firearm or suppressor, IE: not a business ?
Cheers !