In order to ensure compliance with this law, employers must verify that their employees are authorized to work by having them complete Form I-9, which contains certain personal information.

Police requested a records check from his employer; among the documents provided was his I-9, which listed the Social Security number (SSN) of another person.

Kansas did not rely upon his I-9 at trial, but on the other forms, which included much of the same information (such as a SSN); nonetheless, he argued that such usage was barred.

[4] The Court reached this conclusion by observing that the express preemption provision of the IRCA only prohibits a State from making it a crime for employers to hire an unauthorized alien;[note 1] the majority opinion points out that "laws that impose criminal or civil sanctions on employees" are not mentioned in the preemption provision.

Given that these cases fall into this field, the dissent would hold that only the federal government, and not the States, would be able to prosecute any unlawful conduct that took place.