Libertarians oppose such cards for a variety of reasons, one of which is the impact on businesses, according to David Bier, an immigration policy analyst at the Competitive Enterprise Institute, a libertarian think tank.
"The main objection from a business perspective is simply the risk of penalties and threats," he said. "Employers could be put in a position where they have to verify the authenticity of an identification card, and could face fines if there's a mistake."
Bier also thinks heightened workplace enforcement will fail to address the issue of undocumented workers. "The only proven way to end illegal immigration is a robust legal immigration process, whether guest workers or otherwise," he said.