In other words, there is not simply a sign at the international border that states "Do not enter." If that's all there was, foreigners would simply smile at the sign and proceed to enter the United States in violation of the sign. Instead, the government has to enforce the message contained in the sign. That's where the immigration police state comes into play. The police state is intended to enforce America's socialist immigration-control system.

One aspect of this police-state system is domestic highway checkpoints, the same types of highway checkpoints that are found in countries ruled by communist or totalitarian regimes. 

Under an immigration-control system, it's logical that the government would have agents standing at established international crossing points. That's where they determine if a person has the legal authority to enter the United States. If the person doesn't have such authority, he is refused entry.