Step 1. Navigate to Configure Application>Business Objects>Fields >Pick the field with an associated validation pick-list.
Step 2. Note which business object is used by the pick list.
In this example, the field was using "Display Name of Employee" which uses the Employee business object.
Step 3. Navigated to Users and Permissions>Roles and Permissions>Select non-admin role to limit from adding values to list.
In this example, go to Object Permissions> 101-105 Change-FAQ Status>Employee
Step 4. Scrolled down to "Employee" (indicated by pick-list). Unchecked "Add". Save.
Step 5. Switched to UI and role. Verified that the "Add" button is now off the drop down selection.