How To Lock Down Event Registration Form To Limit Registration to a List

They are worried that the URL will be forwarded within our customer companies and that people who are not on our list will register.

If the URL includes the self-identifying mkt_tok (as is the default for emailed links) and you're using Pre-Fill on the form, then you could lock down and gray out the form input.  A non-malicious user will see they're about to submit as "Jill Executive" and will not be able to change the form fields to reflect their own identity.  (You should of course also note exactly what you're doing, i.e. this event is by invitation only, etc.)  This is only casual, good faith protection: it will not prevent a malicious user from hitting view-source and hacking around the restriction. But it will mean that nobody can accidentally sign up who wasn't on the list.

An example of such a form is here, just takes a couple lines of JS:

Here's a live demo: MktoFoms2 :: Read-Only Form

Now, if you need to offer the signup form to people who don't receive the mkt_tok-enized link, i.e. to direct traffic, then you're going to need something more robust, namely a Lookup Form that first sees if they have certain characteristics, and only then shows them the summit registration form. I've posted in the past about how to use a Marketo form as a lookup form.

You could confirm registration by email after a person fills out the registration form. You'd need 1 email for confirm and 1 email for reject and your invitees added to a static list.

your smart campaign trigger would be fills out form. flow would be send email choice #1 "if member of list = invite list" => send confirm email. default choice => send reject email. Similarly your program status can be change status to registered if member of invite list.

OP please return to this thread to check responses from the Nation.