Add explination that you can't attack other players in The Fringe, but

you CAN attack their bases.

xtrn/tw2/backstory.txt

@@ -112,3 +112,13 @@ far in excess of what can be generated through trading even in outside of
 FedSpace.  There are reports that previously notorious pirate captains have had
 DNA makeovers, purchased "clean" ships, and turned their hand to protecting
 humanity drawn by these massive profits.
+
+Because The Fringe is where the war is being fought, the Federation will
+actively police war crimes - out here you do NOT want to be attacking other
+agents of the Federation.  Protecting your own assets against misuse by other
+captains however is considered acceptable as is commandeering someone elses
+assets.
+
+What this basically boils down to is that - although you cannot directly attack
+other players here - you CAN attack their strongholds and invade their planets
+to secure needed war supplies.