Yes and no. Internet connectivity is required during the initial setup process. After that, it is possible to view the camera over the LAN without internet connectivity as streaming is point-to-point and does not occur through a server. With internet connectivity unavailable, functions such as cloud storage of alert videos will, of course, not be available.
If the camera is connected to a LAN that is internet connected, the camera will be available to be viewed from outside the LAN for an app logged in with proper credentials. There is no way to turn this off from the camera side, although it could probably be prevented with appropriate firewall settings in the local router.