No, once they are full admin of the organization they will have access to everything.
The correct option would be to give permission to specific networks and not the entire organization in this case.
However, as you said, they need to have full access to the organization, so it won't work for you.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.
