Upvote:3
Unlike US Canada doesn't have immigration preclearance so the immigration control you will be passing in Canada.
Upvote:6
No, American airports don't offer preclearance the way Canadian ones do. (The reason is the relative number of airports in each country: the preclearance in a small handful of Canadian cities enables flights into hundreds of American cities. To do it the other way around would be crazy.)
You will clear customs and immigration when you land in Halifax.