“From the beginning, the highway has always lacked grace—those who worship desert gods know them to favor retribution over the tender dove of forgiveness” 

Grace is typically bestowed on those who ask for mercy. There is nothing in Desolation or the Devil’s Highway that suggests that mercy or forgiveness is possible. It is implied that the desert makes everyone and everything hard and harsh, even its gods. If grace—in the form of safety or escape—exists on the highway, it often resembles dumb luck and chaos more than divine intervention. Other people become accidental forces for good, not agents with the power to help. 

“They were aliens before they ever crossed the line” 

The landscape is described as an alien region, not unlike Mars. Therefore, its inhabitants can rightly be seen as aliens. However, the word “alien” does double duty in this context. An alien is both someone from another country, but also someone from another planet. Not only that, the word alien connotes an otherness. The men who crossed that line were already from another country, they existed in an alien landscape, and they were already, at least to the people on the other side of the border, aliens in a legal sense.