I would have thought Liberty would have knowledge of many if not all pirate faction in Siruis. The LSF is an intelligence branch and possibly 'spy' group. Shoot me if I'm wrong. Therefore, they would have knowledge of the other House's local pirates.
Another possible reason is the shipping companies encountering the pirates en-route.
e.g. Bowex takes Gold from Bretonia to Liberty for some reason, they see Corsairs and get attacked. When the transport comes back into port, the report would show who and what the pirates were using. Not to mention Bretonia in this case would upload pirate information into the shipping ships so they can identify factions easier.
I think that covers Liberty somehow not knowing the Corsairs. I asmit they have no presence in Liberty, but every House would share information on criminal factions so they can be eliminated wherever they are.
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Using my above statement, Liberty officials would recognize the illegal(?) weaponry and attempt to dispose of them properly to attack the smuggling ring indirectly (in RP).
I do not condone the actions of the said Liberty craft, they took it too far when they engaged the Junker with that weaponry. Too far.
EDIT: Darn you Turkish, beat me to the punch.:lol: