It's all about the forces involved
If you don't have a policeman on the ground, then on just exactly what do you base your claim to have your laws prevail?
If you display your stupidity on a cruise ship, do you expect arrest to come from some policeman based in the nation the ship is flagged in?
The captain's authority on a ship is high precisely because whenever you get more than a couple of humans together, things tend to get complicated. For a trip lasting years, this becomes a real thing. For a one-way trip, a VERY real thing.
The '67 treaty was a pipe dream when it was signed. Any Moon or Mars colony is going to be a frontier settlement. Issues of law & force are going to be settled based on what the folks on the ground decide to do, outside law be ******. That's particularly important when some joker can disperse the air or water supply permanently and with relative ease.
The only way some particular nation is going to have its laws in force is if it is a military outpost. Again, this is a frontier we are talking about.
Biting the hand that feeds IT
