Meeting organizers can choose whether to allow attendees to forward a meeting invitation to others. The option to prevent forwarding is currently only available in Outlook on the web and Outlook for Windows, for users with an Office 365 subscription.
— Read on support.office.com/en-us/article/prevent-forwarding-of-a-meeting-8cd354e5-b319-403e-8dd2-88b8ee89b4dd