When it comes to the topic of immigration, much of the focus is on the individual. A person is trying to get into the United States, and they must complete certain processes in order to make that happen. Immigration is inherently a topic that deals with individuals -- though that's not what immigration is all about.
Consider employment immigration. Yes, this deals with individuals who are looking to enter the U.S. on the grounds of an employment opportunity. However, there are also major implications for the employer or company that brings this individual aboard as an employee. There is a lot of paperwork that needs to be completed on the part of the employer to ensure this individual becomes an employee. The employer may need to endorse or support the individual to allow the person to enter the country.
Ultimately, one of the big elements of employment immigration for the employer is I-9 compliance. The company needs to fill out and complete an I-9 form for every employee who works for the company, and this I-9 form must be approved. However, this form only applies to people who are actually hired -- not people who apply for a job and ultimately don't work for the company.
I-9 compliance is a major part of being an employer. You risk penalties if you are not I-9 compliant. Of course, there are extenuating circumstances. For example, if you properly completed an I-9 and had no reasonable evidence to question an individual employee's status, then you probably won't be punished if it is discovered that he or she is not authorized to work.
Source: FindLaw, "Immigration and Employment Eligibility FAQ," Accessed Nov. 7, 2014