Targeting through group members

Not sure if this is bug, or just an oddity of the targeting system, but…
When an opponent is covered up by someone in your group, you can target the opponent with a spell, but you can not target them for an attack. If you click on them through your group member, you will stand still for the round (I cannot recall if you attack if you are attacked).

what happens is you target your group and does nothing because you cant attack them, however you can target for some reason.

It appears you can also target items dropped in the cloud and you get the same behavior.