"a Latino citizen studying at Arizona State University, whose New Mexico driver's license would not be accepted as proof of citizenship under the law"
Keep repeating that, then ask why the officer didn't accept it. There is always two sides to every story. And this who;le case sounds like a story.
"and a Jamaican immigrant, who fears police will not believe the photocopy of a judge's order that he be allowed to stay in the country, the only paperwork he has that gives him legal status here."
Now I'm not an immigration expert but I believe you need more than a photocopy of some judicial order to be in the USA. Like a passport with a Visa, or maybe a greencard, how about a student Visa.............
I don't think it's legal to ask em as a citizen to prove I am one---at a traffic stop for a civil offense.
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Why All Americans Should Carry ID Papers - Christopher Dickey - Newsweek.com