Val Verde County Sheriff A. D'Wayne Jernigan and other border sheriffs went to Washington to speak to DHS chief Michael Chertoff:

"When we met with Secretary Chertoff, he assured us there would be no action taken on the fence along the border without conferring with local officials... The Secretary told us that he believes that in some areas there does not need to be a fence, especially in places where there are natural borders like the ones we have here in Val Verde County. We told him that the only thing he is going to do by building a fence here is create a firestorm of controversy..."

...Jernigan said Chertoff told the border sheriffs their best route to quash the fence plan is to keep in close contact with their elected representatives in Washington.

"He told us, 'I'm under mandate by that law that says I have to build a fence.' And what he said was, that we need to start lobbying and we need to start informing our legislators so they can change the law..."

Certainly, in some areas the fence might not make sense or might not be necessary due to the local topography. However, I suspect that Chertoff isn't just thinking of those cases.