# ...
# There are models Subscription and MailList defined above.
# MailList has a many to many field 'managers'. This field
# defines which manager is able to edit/add subscriptions to
# a maillist.
# 
# To filter choices in the Django's admin, I use following code:

class SubscriptionAdmin(admin.ModelAdmin):
    list_display = ('id', 'mail_list', 'email', 'name')

    def get_form(self, request, obj=None, **kwargs):
        form_class = super(SubscriptionAdmin, self).get_form(request, obj = obj, **kwargs)

        class ModelFormWithPermissions(form_class):
            def __init__(self, *args, **kwargs):
                super(ModelFormWithPermissions, self).__init__(*args, **kwargs)

                self.fields['mail_list'].queryset = \ 
                    MailList.objects.filter(
                        managers__id = request.user.id
                    )   

        return ModelFormWithPermissions

site.register(Subscription, SubscriptionAdmin)

# This code creates a special ModelForm class which know
# about the current user, his 'id' and permissions.