To assess the claim, O'Reilly talked to retired ICE Special-Agent-In-Charge Claude Arnold, who said he "routinely" arrested illegal immigrants who had voter registrations.
"I worked in six locations across the United States. I probably arrested more than 1,000 illegal aliens in my career and I routinely encountered people who were in possession of voter registration cards. And as a part of my interview of them when they were arrested, I would ask them, "Do you or have you voted?' and often, I would get the answer 'yes,'" he explained.
Arnold agreed with O'Reilly's statement that "it's easy to do it and it's being done."
Arnold said that there is a very high demand for counterfeit documents like a drivers license because a large swath of the illegal population want to work.
He said there are often several illicit document vendors in neighborhoods with high illegal immigrant populations.
Because some states only require a drivers license number to be recorded to register to vote, or apply for an absentee ballot, the illegal registrations "are not necessarily picked up," he said.
Watch the full interview above.