Make the floppy device to be owned by a group (i.e. group floppy) then add the users which should be able to use the floppy to that group.
Code:
groupadd floppy <-- if this group did not exist yet...
chown root:floppy /dev/fd0 <-- if this device does not have its own group already
gpasswd -a user floppy
<-- add the user to the group