As currently, any player with hostility regarding a nation cant undertake the basic citizen mission to join it. Once in, hostility with ones own nation has no effect whatsoever unless they acquire 75 points whereupon they lose the flag. A voodoo card exists which, if used once every 3 days washes all clean whereupon the citizen can then rack up more hostility, again, without sanction.
One way to gain such hostility is via NPC farming when you hit own-flagged fleets : another is to hit own flag players : both actions can be avoided but we all do them occasionally.
The third case is avoidance of ship tax : once a citizen, you just turn off auto=pay on daily upkeep and never have to pay a penny ever again. As long as you clean down your hostility every 3 days, you never need pay at all. But none of that will prevent you gaining rank, voting, and when ranked enough, proposing votes, gaining governors chairs and bonuses, or even the crown itself.
This seems a bit off-kilter to me : a tax dodger can propose and vote on the spending of taxes income they have never paid. A player who freely hits and plunders his own fellow-citizens can rise thru the ranks unhindered. And none of these tax debts are enforcable in any way : there is no means for a nation to sanction such citizens : the citzen can wash away their hostility, the nation cannot add more save revise a law which can adds a mere 1 per hour, requiring over 3 days before it will do anything at all, wasted if the citizen washes themselves, of course : and the debt still remains.
So, I would propose a law as follows :
'Hostility Penalties : (each would be optional and subject to revision votes)
No nation ranking mission can be started if hostility exists between the player and nation.
No nation ranking mission can be completed if hostility exists between payer and nation.
No citizen may vote or propose a vote if hostility exists between player and nation.
No citizen may benefit from a pay-out, or bonus acquired thru rank or nation entitlement, until any hostility between them and the nation has expired.