This reminds me of an experience last week. I was at the US-Canada border in Montana/Alberta walking along the line and interviewing immigration/customs officials. At the crossing point where I was (Del Bonita) there is a small aircraft landing strip, where people in private planes are required to stop and pass through formalities as they fly over the border. The strip is simply comprised of mowed prairie grasses, an orange wind sock, and white and black cones along the edges of the runway. About 90 percent of the runway is in Canada, the rest being just inside the US. As I was moseying around, a man drove onto the airstrip in a truck. His job was to poison the gophers that are creating large holes in the ground, which can be dangerous for small airplane wheels. I followed him and we chatted as he put the poisoned grain in the holes. However, he was very careful not to put grain in the holes that were located on the US side of the border (a matter of about one meter). He said this was a matter of border policy--can't import poisoned grain into the US!! Interesting eh?
Cheers,
Dallen