Originally Posted by
rehoult
Same thing. Officially, you are entering Canada when you go through Customs B; they are just making it quick and painless because they know you will be leaving shortly. But the Visa rules still apply (in both directions).
Edit: There is a limited exception for certain countries who would normally need a visa (
http://www.cbsa-asfc.gc.ca/travel-vo...v-tsv-eng.html)
Well the reverse is not the same thing as the return appears to be a 'sterile' transfer. When you arrive at YYZ from international, you only go to customs B if youre connecting to international. But in this hypothetical case you would be going transborder so you go to customs A then stay to the left. You never proceed through the CBSA checkpoint but rather go up an escalator that drops you inside the transborder connecting luggage area to proceed through CBP checkpoint.