Is there any more clarity on this? I arrived in YYZ yesterday with duty free from DXB. Connecting on a separate ticket to the US today. According to the CATSA website, I should be ok. The person selling me the duty free did not put the receipt IN the bag, although I do have the receipt. The website is ambiguous on whether that's ok or not. Further, how does adding liquid to a checked bag work for preclearance? I clear with hand luggage, am told no liquids, and then exit the US preclearance area to get my bag tagged and come back to drop it off?

Also, where is the list of approved countries available? Is there no documentation?