Summary:

Currently, when a user is removed from a Confluence site, they receive a 403 error on their mobile device but they do not get logged out from the device.

Suggestion:

Our suggestion is to replace the 403 call that is sent from the backend with a 401 call which will ensure that the user is logged out from the devices on removal from the site. 

Note: Even though a 401 is not sent at the moment, the user will not be able to access any data from the site after the user is removed from the site.