The operation to deny access to the task list is only available for task lists created by other users to which the user has been granted access. Such lists have the icon to the right of the name.
To decline access to another user's task list, do the following:
1.Move the cursor over the list that you want to decline access to and click the displayed button.
2.In the menu that opens, select the command.
3.Confirm/reject the denial of access in the dialog box that opens.
You can also decline access to the task list in the list settings change window.