If you order a gun from WGC it will most definitely get seized by customs.
I suggest reading this thread it will give you more info on what you can, and can not import.
http://www.airsoftcanada.com/showthread.php?t=23191
If you really want the WGC M16vn I would suggest checking out the Canadian Retailers link at the top of the site and start sending out some e-mails to see if any of the retailers are willing to get it in for you.
Best of luck,
Autumn