Skip Late Cancel for Subscribers
You can allow any customer with a current subscription or payment plan to be able to cancel any upcoming registrations until class starts. Just select 'Skip Late Cancel' when editing the Subscription or Payment Plan:
Skip late cancel will look at your Cancellation Windows (based on your settings). If a student who has a subscription with Skip Late Cancel enabled will be able to cancel the registration.
When they click Cancel, they will simply need to verify that they want to cancel their registration.