Disable/Enable External devices

I work in an IT environment with many users. I would like to know if there is a way to enable their ability to mount external devices (cds, dvds, flash drives, etc) so they can copy files to the computer, however at the same time, disable the ability to copy files from computer to external media.
Thanks in advance.

The only thing that comes to mind. Is to change the automount options to be read-only.