[proberts]

Your obligation is to employ people who are authorized to work in the US and not to knowingly employ people who aren't authorized to work in the US. So, once you learn that an employee isn't authorized to work, your obligation is to terminate the employment relationship. You have no further obligation to report this person to the government.

[cgb223]

OP here

Obviously the above and below situations are hypothetical. I am currently between jobs, and have never been an employer.

Let's imagine I was aware that a coworker is an illegal immigrant. Do I have any obligation to take some kind of action?

Would it make a difference if one of the C-level employees was the illegal immigrant?

[blorsh]

If your non-action could be construed as sheltering/encouraging/aiding the illegal alien with employed in the USA, you're committing a felony. Other coworkers could of course report you for that felony. Here:

http://www.fairus.org/issue/the-law-against-hiring-or-harbor...