A study from the UC Berkeley Law School's Warren Institute on Law and Social Policy says that creating an identity for all legal American workers using fingerprints or vein scans is a bad idea.

Requiring all workers to get a biometric card to verify their right to work would cost the United States at least $45 billion, infringe upon civil liberties, hurt the poor and fail to stop illegal employment, according to the report.

"This would be a radical shift in our employment system," said Aarti Kohli, the institute's director.

Kohli said the biometric worker card carrying unique physical markers is "an idea that's come up again and again from different political leaders, and it keeps coming up."

Along with costs, Weinberg's biggest concern is the societal impact and privacy.

"It's inherently dangerous and problematic to give government that kind of lever over people, that with just a (computer) switch, you're not allowed to work for a living," Weinberg said.

Such libertarian concerns may be overblown, according to immigration control activists who point out that the government and private companies already collect volumes of personal information, but argue that it would be useful to have it stored in a central database.

"The only information accessible by an employer should be whether the prospective hire is eligible for employment," says Virginia-based Human Resource Initiative for a Legal Workforce on its website. "Employers want certainty in their workforce."