While playing a game a scenario arose where Biggs Darklighter's X-Wing was not in the firing arc of Darth Vader but Horton Slam's Y-Wing was within the arc. Biggs and Horton were within range one so according to Biggs' card : Other friendly ships at Range 1 cannot be targeted by attacks if attacker could target you instead. My contention was that Vader could not shoot at Horton because he could target Biggs (via target lock) just not shoot at him. Is my contention correct or am i over reading the card?

Papa, I think you got it wrong. Biggs could not be attacked so his Special Ability would not help Horton.

Target Lock is an action. Biggs' card says "cannot be targeted by attacks if the attacker could target you instead". They don't reuse the word attack the second time but that is the implication. Step one of the combat phase is "Declare target" which says that it must be in range and inside the firing arc.

So since Vader can't declare Biggs as a target he's free to target Horton. It's one of the good uses of a barrel roll if the roll will take Biggs out of your arc but leave another target within it.

Thanks for the quick answers. It was the conclusion we came to as well just wanted to be sure.