The Iowa Department of Transportation issued the plate to John Miller five years ago, the Des Moines Register reported. Apparently, it took officials quite a while to decide that the "F" is short-hand for a naughty word.
The department decided to take action after they received a letter from Joel Paulson of Ames about the plates.
"'F NADER' is obviously this Corvair owner's response to Ralph Nader's charge against the Corvair. I don't believe I should have to explain to my children about 'F NADER,'" Paulson wrote.
Nader, who has run as a third-party candidate for president in most recent elections, first gained national recognition in the 1960s with his crusade against the rear-engine Corvair and his book "Unsafe At Any Speed."
Miller said he did not intend the plate as a slur, describing it as an in-joke among Corvair fanciers. But he has been ordered to turn the plates in with the promise of a free vanity plate of his choosing or a $50 refund and a standard plate.