Enterprise accounts have the ability to limit which projects users can view.
Only team members who do not have Admin permissions can be removed from viewing a project. (Users with Admin permissions will always be able to view all projects.) 

To access the Team Viewing feature for a particular project, first open the project, then click Project Details. 

This will open the Project Details panel. At the top right, under "Team Viewing", select Change Settings. 

This will open a second window with a list of all of the users in your account. Select or deselect the users you'd like to add or remove from the project. 

Note that there is no way to deselect an admin.  

Click 'Submit' to update these changes.

Please let us know if you any further questions!