Originally Posted by
LarryJ
Each country comes up with their own rules. That's why you have to clear TSA screening after landing in the US from an international flight before boarding a domestic flight. It's definitely worth checking on the other country's rules before you go so that you want be surprised at the checkpoint.
It is also because you have been in contact with your checked luggage and enter a non-sterile area, long before there was ever TSA.