Unenroll users through other method than their original enrollment

Hello.

I want to unenroll users through a different method than their original enrollment method. For example, the user was enrolled through self-enrollment. I want to unenroll him through flatfile.

It looks like the moodle code requires the user to be unenrolled through the same method (at least for flatfile). That means I cannot unenroll a self-enrolled users through a flatfile.

Where and how do I have to change the moodle code to allow such an unenrollment through a different method?

Thank you