If a player attacks a player/npc of that nation, a fine of 20% of their profit is deducted and sent to that nation.
Or
Hostility Fines
A player pays (X hostility w/ nation)*100 to the national treasury.
Basically, if I'm in France an I gain 7 hostility with France (my home country), I have to pay 700 gold coins to the nation of France. The max being 7,500gold. Countries can change the "*100" part per rank. So the King of X Country might be *1000 with a hard limit of 750,000gold in fines.