I just had my shipment of 3-Ad returned to Nutraplanet containing 3-AD, Animal Pak and a few other supplements.
The reasoning behind the customs seizure was because of the ingredients containing, L-carnitine and Androsterone which are both illegal in Canada, so I'm told. That being said, I think it's luck for the most part, depending of you're method of shipment and customs broker.
Also a tip, according to my Fedex Customs broker, is to have a good 3rd party broker setup before hand when trying to bring 'health foods and supplements' across the border.