Just a thought.
Planets with mooring fixtures (which will still have to be there in order for trains to moore) are all police owned (most of the stations who have a mooring fixture are too)
Factions (clans) have to wear their licenses on every ship they fly.
If you make police factions being hostile to pirates from the beginning. Pirates will not be able to dock on those planet, unless you give the option pirates can change their status to neutral to police.
If pirates can not dock on planets, what sense does it make for pirates to own a train?
There would not be a single trade run be available for pirates. (pretty much screwed)