Sorry I can't answer that for sure, on first though I would expect that it would be returned to sender, and you should be able to get your money back..... On second thought, they probably could care less and just throw it in the garbage. Why would some CBSA employee think to send it back, or even care if you get a refund for merchandise not delivered??
Funny that would happen though, as it isn't a banned substance in Canada.... You could try to fight it, and should win, but is it worth the hassle?? Any
e-liquid can be bought and sold in Canada, and there are many Canadian sellers/distributors. The
e-liquid with nicotine is kind of a gray area, but is not banned, and plenty of Canadian suppliers are legally selling it. Not sure on what grounds they refused it, as it hasn't been out right banned, or allowed either way. I know some would like to see it banned, but don't think it can be logically justified as long as tobacco is legal, and absolutely proven to be more harmfull and dangerous to use.
That being said, logic is not always part of the equation when regulations are formulated, so I would not be surprised to see e-juice prohibited, while tobacco products remain legal. Currently there is no law against or for e-juice that contains nicotine.
Order from a Canadian supplier and you'll get what you need. Just by-pass the over jealous border agent who is willing to prohibit a legal product from entry.