Originally Posted by Lstudent
You wrote:
"The same way they ascertain and arrest US citizens suspected of violating our laws. They either have an exigent circumstance, suspicious behavior, tip, investigation, a search warrant or an arrest warrant."
This is circular because of all of the methods you listed "exigent circumstances, suspicious behavior, tip, investigation, a search warrant or an arrest warrant", SPECIFIC FACTORS are needed in order to employ any of these methods. Please, aside from the tip, list specific factors that can be used to give law enforcement probable cause to ascertain whether an individual is illegally present in the United States.