I am trying to use the map to kml conversion tool in a python script. The mxd I provide as input, contains data coming from map service layers. I have no security enabled to that particular layers. I also try to run the specific tool in ArcMap providing mxds that contain layers coming from a map service but I get the same error:

Unable to open MXD - The document contains secure (password-protected) layers.

If I run the same tool with an mxd that contains data coming from a local geodatabase, but not from a published service, it works properly ?

Can anybody tell me why the map to kml tool does not work with map service layers?