Control of the encryption of data for storage with respect to removable data storage cartridges having a recording media and having cartridge memory with at least a portion lockable to read-only, employs the steps of inspecting the read-only portion of the cartridge memory of the removable data storage cartridge for an “Encrypt-Only” flag. If the “Encrypt-Only” flag is present, writes to the recording media of the removable data storage cartridge are limited to data in an encrypted format, if any; and, else, writes to the recording media of the removable data storage cartridge are allowed for data in any of encrypted and unencrypted formats.