Hey @salahy,
For this reason, I recommend using Manual Approval for the meeting so that you can control who is admitted into the meeting. Here are some steps that might help if you have a list of emails that should be admitted to a meeting:
- 
Listen to the meeting.registrant_created webhook
 - 
When the event fires, compare the registrant email with the list of valid emails you have for the meeting
 - 
If the user is on the list of valid emails, use the Add Meeting Registrant API to approve the registrant
 
Let me know if that would work for your use-case.
Thanks,
Max