Turning away potentially underage drinkers is encouraged (and not doing so badly punished) but denying someone legal allowable employment is subject to litigation.
"ANTI-DISCRIMINATION NOTICE: All employees can choose which acceptable documentation to present for Form I-9. Employers cannot ask
employees for documentation to verify information in Section 1, or specify which acceptable documentation employees must present for Section 2 or
Supplement B, Reverification and Rehire. Treating employees differently based on their citizenship, immigration status, or national origin may be illegal."[0]
"ANTI-DISCRIMINATION NOTICE: All employees can choose which acceptable documentation to present for Form I-9. Employers cannot ask employees for documentation to verify information in Section 1, or specify which acceptable documentation employees must present for Section 2 or Supplement B, Reverification and Rehire. Treating employees differently based on their citizenship, immigration status, or national origin may be illegal."[0]
[0] https://www.uscis.gov/sites/default/files/document/forms/i-9...