Third party registration by Moderators Only

I have a situation where I do not want to allow the general public to register on my site. However, I want to allow moderators (who are obviously already registered and belong to a specific ACL group) to fill out the Registration Form for new members and initiate the registration from inside the site, while logged in.

How do I allow my moderators to do this while still allowing them to use the custom registration form that I have designed for new registrations? I dont want the new user to be forwarded to a registration page. I want the moderators to complete the registration process, with the end user only receiving a welcome email at the end of the process.

From backend you can have them use CB > User Management. If you really need this for frontend the best I can suggest is to have normal publicly accessible registration then create a Text field with the following validation.

Authorized input: Custom PERL regular expression
Perl Regular Expression: /^SECURITY_CODE_HERE$/

Replace SECURITY_CODE_HERE with an alphanumeric security code. Next give the code to your moderators for them to input during registration. Ensure the field is on a tab that is accessible to Special only (this will be ignored for registration, but it'll hide the code in profile edit/view properly).

So for example my code could be: s9f74n
Resulting regex: /^s9f74n$/

Now the moderator would just supply that during registration and it'd validate. Anything but that code would invalidate and registration won't complete.

Note they need to be logged out to use registration on frontend.

The alternative is to develop a 3rd party extension that uses CB API to register a user.

Ok. So assuming my moderators are logged in, I would give them a link that says "create registration", which would log them out.

But is there a way to have a "logout redirect" action (attached to that menu item) that redirects only my moderators to the registration form (based on ACL or other profile attribute).

That way I can have a "logout" link simply for logging out (for all users and moderators). And a "create registration" link that will log my moderators out and redirect them to the form.

Navigating to the registration page while logged in won't log them out. There's also no trigger fired before the login check so you can't force them to logout with CB Auto Actions. They'll need to manually logout then go to registration.

So there is no logout redirect that I can attach to a menu item? Do you know of any extensions that will do this (with menu item that will redirect to a specific link upon logging out?)

The login/logout action that CB Auto Actions provides can specify a logout redirect, but it needs a trigger to act on and I can't think of one in CB 1.9 that'd help with this. For CB 2.0 there's new triggers that'd be able to handle this scenario though. As for menu item there is a logout menutype, but you can't specify a redirect.