We learned this years ago. The NSA records everything.
When you live in a city for a while, you get to explore lots of nooks and crannies that visitors never get to see, or they are too distracted by the scenery to take a good look and really see it. The city is encompasses a river delta with two main branches of the river if you don't count the several islands found in all the way up the Fraser Valley. And there are two fjords one of which stretches way inland and has two branches (Burrard Inlet, Indian Arm) and then there is at least one tributary river, the Pitt river, that is navigable.
All of this makes for a very long sea front a.k.a. border. And there are dozens of ports all over the place, most of which are not even recognized as ports by most observers. For instance a barge port which handles barges which are towed by tugboats to the many islands including the big one (Vancouver Island). There is no way to police this border completely. And since there is tons of domestic traffic like those barges, there is a large area where you can't really distinguish between international and domestic traffic.
Shopping in Vancouver with the mind of a hunter gathererer will lead you to all kinds of interesting shops. Some obviously selling smuggled goods. Some obviously supplying people who do not speak English or have any knowledge of Canadian culture. In other words, you can tell when shops cater to illegal immigrant workers and not to local Canadians.
I look around as I drive along the rivers and the fjords and there are so many places where you could land a cargo at night and nobody would notice. Containers can be made watertight, dumped overboard in international waters, scooped up in the dark by domestic traffic, and landed up river away from prying eyes. Seattle should be roughly similar. And don't get me talking about the Great Lakes, particularly areas where there are lots of islands to block the view of Coast Guard patrols.