As of version 2.2, there are tools available to help you use Registrations for the Events Calendar in compliance with GDPR. You can now add a checkbox field to require attendees to opt-in to terms and conditions as well as link to a terms and conditions page right beneath this field.

You can also export personal data attached to specific email addresses used when a person has registered and delete all data attached to an email address.

Read more about these features here: https://roundupwp.com/gdpr-compliance-with-registrations-for-the-events-calendar/#free