If you'd like to have public events approved before they are published, you can turn on the Approver Feature. This is done in the jmx-console.
Once Workflow is enabled, the Approval Queue tab will appear in the admin client, and non-approvers will only be able to Add Events (they will only see one button). See the Administrator roles page for instructions on setting the approver role.
Users who are not approvers will no longer publlsh events directly into the calendar. Any events they create will be stored in a separate events collection that isn't visible to the public. Approvers will see those events in the Approval Queue where they can inspect them, perhaps update them, and publish them to the calendar.
If you are using a different version, please click on "Click for all versions" on the left side of the page and select the relevant version.