Hi,

In your case it seems that, you need a group of users to see List View only where as Other group user have to see Both the List View and Form. In this case, assigning groups for the Views wont work out. 

What you have to do is that, define two different menus and give separate action for both menus and specify the available views in the menu action. Then you can specify List view in one menu action and tree, form in the other action and link it with menus and hide the menu based on the groups. You can give groups="external_id_of_group" along with menu.

Thanks