Write Protect and SD card

We are using 8 GB Class 10 UHS-1 to store important data. Our customer would like us to write protect the card after the data has been written. I have read on other sites that there is a way to PERMANENTLY write protect an SD card using SDIO cmds. The SD cards are in an embedded system and would like to have the embedded software write protect the card before extraction. Anyone done this kind of thing???