Custom Role to prevent user NOT to edit Lead Database Smart Lists

Hello Every one,

I m trying to create a custom user role where the user can have read-only access to the lead database, but not edit the smart lists.
I tried creating one custom role & gave just the "View Opportunity Data" option alone and not giving any of the other Lead Database options like "Edit, Delete, Merge, Export Leads/List".
But still the user have permission to edit all the custom smart lists created.

Is there a wasy to prevent the same?

Thanks in advance for all your ideas.
Vidhya