All U. S. companies have to comply with the federal requirements around the form I-9. The Form I-9 is for the purpose of Employment Eligibility Verification to ensure that the employee(s) a company hires are eligible to work in the United States, whether as US Citizens or with an authorized work permit/visa. The Form I-9 must be completed in full by both the employee and the employer with the completed forms maintained separately from the regular employee files.
http://www.tirereview.com/Article/116176/immigration_compliance_requirements_for_employers.aspx
