It also helps to have a Y38 Form from Customs Canada. This is NOT provide any protection from seizure but it does prove to the customs agent that you bought this AEG, $300 sight, etc... in CANADA. I've used it a few times when attending Pine Plains and I've not had any problem. Plus I find in just presenting the Y38 with your passport signals you've done your due deligance.
Here is link that might help.
Plus theres a few posts on the forum somewhere