Removing a file from a protected folder in Mojave

You can remove the file without disabling SIP by booting to Recovery and then deleting the file in the terminal. The system disk is actually mounted read/write in Mojave Recovery, so the trick is that you have to refer to the drive by starting at /Volumes/yourdrivenamehere. So in this case the command to remove the file would be:

rm -rf /Volumes/yourdrivenamehere/Library/SystemMigration/History/Migration-1C2FCFF8-A394-409D-8DB3-E7885C0D5E81/QuarantineRoot/Library/StagedExtensions/Library/Extensions/Soundflower.kext

You will need to disable System Integrity Protection and remove /Library/SystemMigration/History/Migration-1C2FCFF8-A394-409D-8DB3-E7885C0D5E81/QuarantineRoot/Library/Extensions/Soundflower.kext (and then re-enable System Integrity Protection).

To enable or disable System Integrity Protection, you must boot to Recovery OS and run the csrutil(1) command from the Terminal.

• Boot to Recovery OS by restarting your machine and holding down the Command and R keys at startup.

• Launch Terminal from the Utilities menu.

• Enter the following command

  csrutil disable 
  

  (or crsutil enable)