If the event coordinator needs to cancel a student's registration, you can do so by choosing Registrations from the left side of the page and then clicking Registration Reports. You should then click the Student List for the event in question. You will then see a list of all students registered for that event and can click the Cancel button in the Actions column as shown in the below example.
Once you click the Cancel button, a screen will open where you can enter or edit the cancelation fee plus enter a note as to why the registration is being canceled.