They count the Great Lakes as well, including all of the Michigan lobe of Michigan-Superior. I'm a bit surprised they don't also count everywhere within 100 mi

They count the Great Lakes as well, including all of the Michigan lobe of Michigan-Superior. I'm a bit surprised they don't also count everywhere within 100 mi of the doors into the international terminals of every international airport. If you're going to set an arbitrary limit without legislative oversight, why not set it in a way that maximizes your agency's own power? What's magical about 100 miles, anyway? It seems very suspiciously based on a power of ten of a specific unit of measure, and not on any real distance that may be supported by statistics or analysis. I'd say draw the line where you have a 95% certainty that any persons encountered on the border side of it just crossed over. Which is to say that the border patrol would have to stay on the border side of any major highway, and would need to pay attention to where the boats come and go.