So my noble (barony) just punished about 13 citizens for either violation of production order, or more frequently for violation of export prohibition (or both, in one case). She had a production order (make bracelets) before the caravan arrived, and I fulfilled that. About when the caravan arrived, she removed the mandate and had no mandates, so I traded. I traded what I usually do, hundreds of human, elf, and dwarf trophies (crowns, earrings, bracelets...) that were dropped by a goblin in my drowning trap (originally there were 3077 trophies, now I've atom-smashed or traded most of them away). AFTER I was done trading (some times after, but not after the caravan left) she prohibited the export of bracelets, and I thought I was fine because I had already traded them. Now, some months after, I'm getting job cancellations, I find out a few dwarves were imprisoned, I check the justice screen, and 1/4 of my population is scheduled for prison time for the reasons I already mentioned... WHAT IS GOING ON?!? My fort won't survive this unfair justice, and so I reverted back to my previous save before all my dwarves were guilty. Also, my barony is the one who traded, in case that means anything here.
EDIT: Found some info on wiki, but will it happen again if I just seize the caravan so the bracelets don't leave the map? Or is the caravan possessing them at any point of time enough to trigger this?