Zoom Apps External User

How can I turn off the ability for external users to use third-party apps from the Zoom Marketplace?

An organization-internal user is claiming that an external user has been using a third-party app in meetings hosted by one of our internal users. For internal users, any and all apps must be approved by an admin, but I cannot find a setting that limits the permission of outside members. If this is not possible, it would be a security-friendly feature for organizations to control the apps that interact with our meetings.