I am unfamiliar with any legislation making that illegal. Regardless, the paper record could just be used to allow voters to verify their vote, and then returned upon exiting the polling booth or station, removing any possibility of external coercion. The voting machine could have a receipt scanner, and insertion of the receipt, could be used to validate their vote.

Most of the screw-ups in the 2000 election were because voters had no means of verifying how their ballot would be tallied, allowing many mistakes to be made, such as the 'butterfly' ballots in Florida's Palm Beach county.

Any more objections?