If the enrolment was added via Banner, it has to be removed from Banner too. We can't change it in Minerva - it will always go back to what's in Banner.
If a member of staff needs to be on a module in Banner but doesn't want to see that module in Minerva, use the EXCL staff assignment type code on the SIASSGN form in Banner. By the next day, they shouldn't see the enrolment in Minerva.
Please bear in mind that Minerva enrolments won't be removed for students unless they were added in error - their record of attendance on the module/organisation needs to be kept. Similarly for staff we wouldn't normally recommend removing yourself from Minerva modules which you taught. Removing an enrolment results in Announcements/Discussion Board postings/Grading information becoming anonymous.