Preventing users from changing a repository's visibility
You can prevent members from changing the visibility of organization-owned repositories on your GitHub Enterprise Server appliance.
When you prevent members from changing repository visibility, only site administrators have the ability to make public repositories private or make private repositories public.
In the upper-right corner of any page, click .
In the left sidebar, click Business.
Under your business account's name, click Settings.
In the Business settings sidebar, click Member privileges.