A player attacking a mobile or being attacked by an aggressive mobile, is entitled to do combat with the mobile as it was originally designed.

You may_not_cast any helpful or shielding spells on mobiles, whether they are currently engaged in battle with other players or will engage in combat with other players at some time in the future.

In addition, mobiles with specific functions, like Hometown guards, are equipped to do their job, without the assistance of players, and should not be assisted by way of helpful or shielding spells.

*Information as of July 27, 2005