Actually take ethics into account when trading stuff at settlements.

[GoblinCookie]

I have found out that I can sell controversial things like human leather and slaves even to factions that do not believe in things provided I travel to their town.  In a manner of speaking it makes sense, obviously I am selling to criminals within that faction rather than the faction itself but really it shouldn't be that easy. 

Instead of always being able to sell illegal stuff, how-about we randomly determine whether illegal goods will allowed to be sold every time a town's inventory restocks, using a separate trade screen called the 'criminal contact screen'.  The odds of this screen becoming available depends upon the settlement (not the factions) crime value in a simple fashion, the crime value is your odds of a criminal contact spawning when the town's inventory restocks. 

A town's has a base crime value which is determined pretty much solely by how many things it's faction is against that involve a 'material component' that can be sold.  Some banned things (like drugs) are considered less niche than other things (like human leather) and so prohibition of those things entails a higher base crime value, but all banned things entail some extra base crime. 

The crime value goes up due to other contextual factors.  The most basic faction is goods sold to the illegal trader of that town; so if you sell a lot of goods to the criminal trader then he is more likely to show up next time.  Other factors are.

1. The presence of each pirate base within a certain distance. 
2. The presence of any non-hostile base in a certain distance that legally sells goods illegal to the base's faction.  This potentially includes the player. 

There is also a suspicion value.  The base suspicion value is 10% for a neutral faction and 1% for an allied faction.  Suspicion is your chance of the 'criminal trader' being an informant and selling you out.  If you get caught, it harms relations with that faction and results in a 'trading ban' in that town for a given period that prevents all commerce, legal or otherwise.  Suspicion also goes up for the following reasons.

1. Every other base of the same faction within a certain distance.
2. Every completed interaction with the criminal merchant raises suspicion. 
3. Suspicion is earned for each ethics divergence between your faction and theirs.
4. Suspicion is earned for every other base within a certain distance whose ethics diverges from the base's controlling faction's ethics in the same manner.  Ie. If you are a cannibal and they are not a cannibal, then any other cannibal bases within a given area raises suspicion. 
5. Suspicion gain from dealing with the criminal merchant is multiplied for every separate infraction you make.  If you sell human leather AND drugs, this incurs more suspicion than if you trade only in one of these categories. 

[zgrssd]

Such a limit should only work after we have a option to convert factions or at least whole settlements to our religion. Otherwise there would be no way to interact with the mechanic. It would simply be a wall you hit with no counterplay.

In the meantime, consider that the traders might have stuff that is illegal in their faction - to sell it to 3rd parties.
There is a difference between transporting goods into a country or through a country.

A good starting point might be the wandering traders consider what you want to buy when their inventory is generated:
https://ludeon.com/forums/index.php?topic=54704.0

[GoblinCookie]

The idea is to make it generally better to trade with factions that agree with our values.  The 'counter-play' is to move to where a faction exists that agrees with the products we are selling.  Or go to several settlements in a row, hoping that one of them has a suitable source.  Smuggling is meant to be harder and riskier than selling legitimate goods.

I am not sure what legal systems you are use too but no.  You cannot legally buy items that are illegal in one jurisdiction in order to sell them on to another jurisdiction where they are legal.  So the third-party stuff you are referring to is criminal smuggling, I already took that into account in my OP did I not?

Crime value in the faction (the odds of having a criminal merchant is increased by).

1. The presence of each pirate base within a certain distance.
2. The presence of any non-hostile base in a certain distance that legally sells goods illegal to the base's faction.  This potentially includes the player. 

[zgrssd]

I am not sure what legal systems you are use too but no.  You cannot legally buy items that are illegal in one jurisdiction in order to sell them on to another jurisdiction where they are legal.  So the third-party stuff you are referring to is criminal smuggling, I already took that into account in my OP did I not?

How did you missread it like that?

Place A it is legal to buy/sell
Place B it is illegal to buy/sell, but not to transport through.
Place C it is legal to buy/sell

You buy at A
Transprot it through B.
To sell in C.

And before you wonder, a traders warehouse might be considered a seperate jurisdiction from the country it is in.
You meet 5 minutes outside of town borders. Transfer the goods and silver there.
Trader Resident in B moves the goods to a Freeport in B without ever selling in B. Legal.

[GoblinCookie]

How did you missread it like that?

Place A it is legal to buy/sell
Place B it is illegal to buy/sell, but not to transport through.
Place C it is legal to buy/sell

You buy at A
Transprot it through B.
To sell in C.

And before you wonder, a traders warehouse might be considered a seperate jurisdiction from the country it is in.
You meet 5 minutes outside of town borders. Transfer the goods and silver there.
Trader Resident in B moves the goods to a Freeport in B without ever selling in B. Legal.

Not relevant I am afraid, because we aren't transporting through anything, that is essentially legal in my suggestion.  We are actually buying/selling the goods in question in the jurisdiction of said faction.  There aren't any free-ports in Rimworld and there aren't going to be (not enough commerce), so the legal shenanigans you speak of are not relevant. 

[zgrssd]

How did you missread it like that?

Place A it is legal to buy/sell
Place B it is illegal to buy/sell, but not to transport through.
Place C it is legal to buy/sell

You buy at A
Transprot it through B.
To sell in C.

And before you wonder, a traders warehouse might be considered a seperate jurisdiction from the country it is in.
You meet 5 minutes outside of town borders. Transfer the goods and silver there.
Trader Resident in B moves the goods to a Freeport in B without ever selling in B. Legal.

Not relevant I am afraid, because we aren't transporting through anything, that is essentially legal in my suggestion.  We are actually buying/selling the goods in question in the jurisdiction of said faction.  There aren't any free-ports in Rimworld and there aren't going to be (not enough commerce), so the legal shenanigans you speak of are not relevant.

Except the Warhouse might be legally outside the Jurisdiction of said faction, despite being physically in the Factions territory.

Stuff like that happens in the real world.
It happens on the Rim. Especially with religious mandates.
You were going for a realism argument. But my realism is bigger then yours 

I am all for it, if we have more counterplay then just "do not settle anywhere near them". Some "conversion missions" would be all that is needed.

[GoblinCookie]

Except the Warhouse might be legally outside the Jurisdiction of said faction, despite being physically in the Factions territory.

Stuff like that happens in the real world.
It happens on the Rim. Especially with religious mandates.
You were going for a realism argument. But my realism is bigger then yours 

I am all for it, if we have more counterplay then just "do not settle anywhere near them". Some "conversion missions" would be all that is needed.

That isn't how freeports work, only embassies work that way.  Freeports do not exist outside of the jurisdiction of anyone, they are simply places exempt from paying import taxes, so if it is illegal to buy, sell or possess something in the wider country, it is also illegal to do this in a freeport. Granted creating freeports is in most cases dumb, particularly those at geographically 'premium' strategic locations (the Suez canal), but we aren't here to discuss politics (freeports is basically like giving people free rooms at your hotel). 

Whether we pay import taxes in Rimworld is an interesting question.  Import taxes could explain why it isn't cheaper to buy from a town than it is to buy from a caravan.  If there were freeports in Rimworld, they would all be in orbit since nobody would bother to actually 'land' the goods if they wanted to ship them to somewhere else via our world, as getting goods back from a planet is pretty expensive once you have landed them.  I think they use some kind of teleporter to manage it, as I recall the last time I actually set up an orbital trading beacon. 

Conversion mechanics are a separate topic.  Possession of illegal goods remains 'legal', so our base does not have to worry about 'settling near somebody' and we are independent (why we piss them off by settling with 5 squares of a faction, because we stole the land we settled on).  My idea is simply that the traders in a town should refuse to buy the goods that are illegal.  We would however have a random chance of having a separate criminal trader (different interface) that only buys illegal goods but dealing with this criminal trader carries a small % chance of getting caught. 

The only punishment is that we get banned from trading in that town's marketplace for a certain period of time.  We can still trade with other towns, even from the same faction.

[zgrssd]

Except the Warhouse might be legally outside the Jurisdiction of said faction, despite being physically in the Factions territory.

Stuff like that happens in the real world.
It happens on the Rim. Especially with religious mandates.
You were going for a realism argument. But my realism is bigger then yours 

I am all for it, if we have more counterplay then just "do not settle anywhere near them". Some "conversion missions" would be all that is needed.

That isn't how freeports work, only embassies work that way.  Freeports do not exist outside of the jurisdiction of anyone, they are simply places exempt from paying import taxes, so if it is illegal to buy, sell or possess something in the wider country, it is also illegal to do this in a freeport.

Since nobody but themself know is in them, how do you know they do not harbor illegal or forbidden material?
How do you know those materials have not changed ownership?

[mlzovozlm]

How do you know those materials have not changed ownership?

even pawns change ownership in Rimworld (￣y▽,￣)╭ try selling base in Ideology and you see ex-pawns coming back as slaves, prisoners, pirates, with different ideoligion occasionally

[GoblinCookie]

Since nobody but themself know is in them, how do you know they do not harbor illegal or forbidden material?
How do you know those materials have not changed ownership?

Well if you can manage to change possession of the item without getting caught, well you are now a successful criminal.  The point of my proposal is not that smuggling activities should not be possible or profitable but that they should carry some risks.  At the moment we seem to be able to engage in risk-free drug-dealing and dealing whatever else.