Sharepoint provides two ways a user can delete an item from any list:
From “Delete Item” menu option available in ribbon
From “Delete Item” menu option available in the item’s context menu
Now you may think that both these options are just alias of one another, i.e. do the same thing the same way which is to delete the item, and must be implemented the same way.
But that is not the case. Both are implemented differently, i.e. both these options use different route of accessing the delete functionality on server. The context menu option uses remoting where as the ribbon option doesnot. So due to this, though you may have given “Delete Items” permission on the list, you need to provide one more permission, “Use Remote Interfaces”, to allow successful deletion from delete item option available from an item’s context menu. Not providing this second permission would lead to a condition where in the user would be able to delete items from “Delete Items” link available in Ribbon, but trying to delete an item from that item’s context menu would lead to an “Access Denied” error message.
Thus, when ever you find yourself into the situation where in the delete from ribbon is working but the same from context menu is giving error,go to the permission level that apply to the list or that item, provide “Use Remote Interfaces” permissions, MISSION ACCOMPLISHED.