If a valid Arizona driver license is acceptable as proof of legal status, why was this truck driver hauled off by AZ law enforcement and detained until his wife left work and went home so she could bring BOTH their birth certificates to ICE?

http://belowthebeltway.com/2010/04/25/arizona-truck-driver-forced-to-show-birth-certificate-to-prove-hes-a-citizen/

[[PHOENIX – A Valley man says he was pulled over Wednesday morning and questioned when he arrived at a weigh station for his commercial vehicle along Val Vista and the 202 freeway.
Abdon, who did not want to use his last name, says he provided several key pieces of information but what he provided apparently was not what was needed.
...

Abdon was told he did not have enough paperwork on him when he pulled into a weigh station to have his commercial truck checked. He provided his commercial driver's license and a social security number but ended up handcuffed.
An agent called his wife and she had to leave work to drive home and grab other documents like his birth certificate.
...
Both were born in the United States and say they are now both infuriated that keeping important documents safely at home is no longer an option."]]