Transporting snakes across the border

[reptiledude987]

I'm considering driving down to the states at some point when theres a repticon event thats not too long of a drive from Ontario. What I'm wondering is what will be involved in bringing an animal back with me. I know some species are easier to get across the border than others. I'm thinking most likely would be looking at some sort of king or bull snake depending on what I find. My question is do I need to get documentation from the seller to bring it back to Canada and what kind of border inspection would be required as I've only ever purchased animals from inside Canada.