By SEAN HIGGINS • 1/4/16 12:01 AM

A new federal guidance for employers illustrates the Catch-22 situation that immigration law creates for them: Businesses cannot employ anybody who is not legally residing in the U.S., but trying to determine if any of their employees are not legal residents can result in the business facing a federal discrimination lawsuit.

In other words, it can be illegal for an employer to try to find out if it is complying with the law.

The Justice Department and Immigrations and Customs Enforcement jointly issued a memorandum on Dec. 14 meant to clarify an employer's responsibilities, although the law itself has been on the books for decades.

"This is the first time Immigration and Customs Enforcement has actually come out with these guidelines in terms of ... what an employer should do when they are confronted with information that someone may not be authorized to work," said Kim Thompson, an immigration lawyer with the management-side firm Fisher and Phillips.

The new guidance says, among other prohibitions, that employers cannot inquire on the basis of a worker's "citizen status or national origin." Nor can they request specific documents or act based on tips. They cannot use the government's E-Verify system after the worker is hired. Even if they do find faked documentation, they cannot necessarily act on it.

"The message is, 'Think before you audit — Is this really something you want to undertake?' Particularly in-house, because it is fraught with landmines," said Beth Milito, senior executive counsel for the National Federation of Independent Business.

The problem arises from the fact that the Immigration Reform and Control Act specifically prohibits hiring people who aren't in the country legally.

However, the government has long held that employers must also abide by various federal civil rights and worker protection laws regardless of their workers' immigration status. In general, the employer must bend over backward to resolve any questions over legal status without firing the employee.

The memorandum, which is presented in a "frequently asked questions" format, shows just how tricky compliance can be.

For example, if the worker used what either appears to be a faked photocopy of an official document or someone else's document, the employer must give that employee an opportunity to present a different one from the government's approved list. The employer is, however, prohibited from requesting a "specific document."

"I don't know about you, but I have never seen a [Native American] tribal card, but that is one of the [approved] official documents," said Angelo Amador, senior vice president for the National Restaurant Association. "If a worker shows that to a restaurant and the manager mistakenly asks for a driver's license or something else, they can get into trouble."

The government's cross purposes mean that employers can find themselves in hot water with one branch of the federal government for trying to comply with the dictates of another.

In September, the Justice Department slapped a $200,000 fine on Nebraska Beef Ltd., a meat packing company, for demanding that employees show proof of their immigration status.

"The department's investigation found that the company required non-U.S. citizens, but not similarly-situated U.S. citizens, to present specific documentary proof of their immigration status to verify their employment eligibility," the Justice Department said in a press release.

At the same time, the memo states that employers are liable for "knowingly" employing an illegal immigrant. It adds, "By regulation, 'knowing' includes not only actual knowledge, but also knowledge that may be fairly inferred." The government is still diligent about checking businesses for employing undocumented workers. Under President Obama, Immigrations and Customs Enforcement has audited the books of more than 14,000 businesses and led high-profile raids against employers like Walmart.

Immigrations and Customs Enforcement spokeswoman Danielle Bennett said it was up to employers to do their "due diligence."

"It is something employers are required to do just as they are required to follow the law when filing their taxes," Bennett said.