For a trade system to work there has to be an enforcable set of standard terms and understandings. That can be a Uniform Commerical Code (if, as I play, the 3I is America in space with dukes instead of senator families); it can be a private insurance, inspection, and arbitration board like the Brits used (and still do sort of); or it can be some other system that provides a set of rules and outcomes to disputes that are clear enough to allow investments to be made at a estimated rate of risk and return.
With the UCC, comes related criminal law. No stealing or hijacking, no killing passangers or crew without reason known in advance. No mutiny. Proper care in operation. The same need for a known outcome means that the 3I will be providing both the trade rules and enforcement, and the releated criminal provisions.
The rules don't have to be fair, but they have to be fairly enforced or if unfair they have to be known in how they are unfair.
If there is a rule that a ship's captain can execute anyone who comes within 8 feet of the bridge valve, that is workable even if unfair. If there is a rule that you need 120% lifesupport for your total crew and passenger load, as long as the investors and insurers know that the rule is enforced except for shipping lines the nobles invest in, who can run at 101%, that is also fine.
Anything else leads to too much risk and no meaningful investments.
There is going to be law in J-Space, but it does not have to be moral law. It does need to set forth terms and conditions of the transport and it has to address standards for the transport--which includes things like endangering the ship and killing your fellow passengers. Anything else added into the law will be judged by the investors as to whether it risks their investments.