So, I've learned that it's perfectly fine to bring garden snails interprovincially via plane, but they need to be handled like any other animal. IE: You cannot bring them in your carry-on, they must be checked.
The Greyhound in Canada does not allow snails at all, as they do not want them in the carriage and animal cruelty laws prevent them from putting them underneath. However, I didn't know this and several years ago I transported about 15 snails in my checked baggage from Salmon Arm to Calgary and they all survived.
You can also just mail them to yourself to ensure that they're handled properly and you don't get any weird hold-ups/looks at the airport... Just at the post-office, haha.
Hmmmm, that's very interesting. Never knew Greyhound actually has rules like that.
you have written: "If you get caught you can plead that some shady person outside the airport had put them in your bag." Sorry, but that's pure nonsense. You are responsible for your luggage, and no one else. If it is forbidden to have whatsoever in your luggage then you have to bear the consequences. Please don't give advices how people might get in trouble (moreover: there are many young and very young people in this forum).