You're under the assumption that every craft is going to understand what a code seven-ten is. Plus, there could be times where someone is simply forced to go into the system due to damage or some other emergency.
It was idiotic not to have exceptions built into the treaty for non-combatants.
Well, wouldn't there be beacons set up saying "Listen, we aren't supposed to go in there."?
The Feds were the ones violating these worlds' Sovereignty, it's more or less a Grey area that the story doesn't draw much attention to.