What gives? Officials often cannot ask a person's immigration status. What??

A statement in an artice in the Gwinnett Daily Post caught my attention.

The article concerns the presentments of the Gwinnett County's most recent grand jury, which presentments found that "there is no way to determine, in any definitive way, how many tax dollars are spent providing county services to undocumented immigrants."

Presentments are issued at the end of each grand jury's term in office, and the presentmens from this grand jury recommended that county commissioners and state legislators try to track the fiscal impact of undocumented workers.

The statement in the article that caught my attention was "[w]hile officials often cannot ask a person's immigration status . . . ."

Can't ask? What do these people think? Are these officials under the impression that being in this country illegally is some constitutionally protected right such as the right not to be discriminated against on account of one's race, sex, religion, national origin, etc.?

Wake up America!