CB has no PMS built it. We integrate with UddeIM. I believe "Moderate new users" maybe what you're looking for on the System tab of UddeIM, but it requires premium plugin purchase from UddeIM from the looks of it and can't be completely sure this is what you need. I suggest posting to the below UddeIM forums to see if the "Moderate new users" is the correct feature, if the feature is elsewhere, or if it can be added.
www.joomlapolis.com/forum/25-uddeim-plugin-and-component