"Undocumented immigrants are able to apply for driver's licenses in the state, which makes it easier for them to mistakenly become registered eligible voters.

"The state automatically registers them to vote unless they check a small box saying that no, they don't want to get registered to vote," LaLota said. "I would presume some of that happens intentionally, probably a larger amount happens unintentionally, but whatever the case is, the end result is a large amount of folks who are not in our country legally getting put on the rolls."

According to the New York DMV website, "the DMV does not approve or deny voter registration applications," but they "send the application to the County or City Board of Elections for their review."

LaLota said his ability to find and remove non-citizens from voter files on the county level was constrained. "I don't have any tools," he said. "I'm not allowed to, as an elections commissioner, ask anybody from the U.S. Department of State or anybody else, who has citizenship, who has a Social Security number or anything else, so I have no tools here, congressman."