Admin approval for user signing up for specific lists?

I'm using FluentForms for all my subscription forms with the FluentCRM integration. 

The newsletter subscription forms add the user to "newsletter 1" list by default. There is also an optional checkbox that when selected, adds the user to another "newsletter 2" list.

Is there a way to configure things to require Admin approval before a user can be added to the "newsletter 2" list?