Unless you tried setting up the shield code somehow so only, say, Team 1 (Rep/Imp) can go through and Team 2 (CIS/Reb) can't, I don't think it'll work if it's only set to friendlies, enemies, etc. Think of it this way: Because of the nature of the game, in which you can choose to be either team,
who are the friendly units? You could play Emps and have Emps go through the shield, then play as Rebs and have the Emps being unable to go through the shield, and vice versa with the Rebs. In short, have it assigned to a team number instead of a player's side.
EDIT: I just realized that my answer wasn't answering the question.

Ok, so it's a workaround suggestion, not a solution to your problem, Redline. If you can't ODF code the shield to do anything like that anyways, then don't worry about it.