Pipelines to the north. Walls to the south. Between President Trump's issuance of a permit for the Keystone XL pipeline crossing from Canada and his promise to build "The Wall," the politics of our national borders rarely have been in as much turmoil as they are today. And as with any infrastructure project, environmental policy has been deeply in play all the way. But the environmental law of the borders might surprise you. Indeed, arguably there isn't any for these two projects.