Restrict access to Categorization Levels in CRM Web UI

Hi All,

I am trying to restrict a field in CRM WEB UI SCREEN.

From the given screenshot I need to ensure that the option "REASON > Category1,2,3,4" should not be seen for a user.

I need to find out the auth. obj. that is controlling the above screen in CRM, so that I can restrict access on the auth. obj.

Could someone please help me find the appropriate authorization object.

Thank you,

Vani