The border

There's a little peninsula called Point Roberts. The northern part of the peninsula is Canada. The southern part is the United States.
Luis is standing in Canada. Behind the yellow barrier is the United States, where there is the sign (on top).
The third picture is Luis and Ken in a different part of the border, which actually has a fence and a marker beyond the fence identifying the international boundary.
But if one follows along the fence to the beach, you get to where Luis is standing in the last pic. He's on the Canadian side of the beach. A few feet beyond is the United States. But, as I said, on the U.S. side is merely a small peninsula, so there's nowhere to go to.