Trading in Renaissance Kingdoms consists on 2 levels. County trade/ town trades, and private person trades. This is also among the levels grants and safety grants being used in allowing people to do this with few to no problems of thief's stealing these goods.
While at the moment, there is/was a county fair which allowed trading among the towns very easily with a 50 pound tax that would go to the county council to help in the management of the county. Currently this feature has been removed forcing towns to either directly sell to the council. Councils of the counties must then form trades for people to go to other towns or counties to sell the goods. This works the same way with town trades.
Private trading on the other hand is merely 1 person taking goods from one town to another to either help the town or attempt to make personal gains. Profiteering in the same town (The act of buying low and selling high) is widely considered a minor criminal act and often is punishable with fines issued by the county judges when sufficient evidence of this act has been gathered.