Well this is interesting...

The US Customs and Immigrations Services "Handbook for Employers" says

Providing a Social Security number on Form I-9 is voluntary for all employees unless you are an employer participating in the USCIS E-Verify Program, which requires an employee’s Social Security number for employment eligibility verification. You may not, however, ask an employee to provide you a specific document with his or her Social Security number on it.

It also says documents from List A (such as my U.S. passport) require no additional documents, employers cannot require more documents than are necessary, and employers cannot tell employees which documents they can present.

I am irritated.