I'm trying to avoid certain group of users using the exporting function in OpenERP v7.0

I'm doing next: I'm adding a rule in the Access Control List for both ir.exports and ir.export.lines objects. Both of them pointing to the user group where users that can't export are. Once added, any of the checkboxes are selected. That must avoid those users to be able to export data, at least that is what I've understood in theory.

The thing is that, once added those rules, if the users try to export they will receive a warning alerting them that they have no permissions, that only certain users can use that function. However, behind that warning, the export window is opened and, when they "accept" the warning window, they can use the export window with no problem, so the ACLs doesn't do anything.

What I'm missing? I thinkd those ACLs are right, I can't see what I'm not doing.