ochd said:
When it comes to areas of chartered space outside the Imperium or other empires, confederations and so on (like District 268 or much of the Trojan Reach), how are things like red-zone interdicts enforced?
Ships on station from whoever red-zoned it. If that's sensitive politically then gunships not capital ships, but something on station.
ochd said:
Starports are said to be Imperial territory, but what about starports in non-aligned systems?
Case by case, but most often a Starport Authority similar to our Port and Airport Authorities. Probably chartered to the local world government. I imagine most ports close to an Imperium border running with the same rights and privileges for ships and travellers as actual Imperium starports just to avoid attracting any gunboat diplomacy.
ochd said:
If a starship is found floating in outer space somewhere in the Sindal subsector, with all people on board dead, then who arbitrates on salvage rights, takes responsibility for investigating it, etc.?
Now this is interesting. I have an answer that satisfies myself, but I'm not aware that it's canon.
If there's one strong Imperium on your map I assume it's Admiralty courts do in fact arbitrate certain cases from outside the normal civil borders of the Imperium law; such is the nature of Admiralty courts. And they do have motivation, if only to confirm salvage as legitimate and not a cover for piracy.
If there's no clear single power on the map things can get more complicated, because the salvagers themselves may prefer some friendly system government. But assume the government the ship was registered with requires you file for salvage with them to release the title. If you only want to gut the ship for scrap, or if you think you have a safe and sympathetic harbor for the whole ship, you can try to skip the paperwork. Odds are good no one's going to come along on patrol in deep space and ask you what the hell. But if you want the whole ship working, or even major systems such as power plant, drives, computer and so on, you're going to want to clear things up with the system of registry or else get flagged any place that wants good relations with the system of registry. So you may as well file with them and clear things up, or you risk getting needlessly tagged as suspected pirates.
In passing, take a look at
marine salvage and
admiralty courts on wikipedia. As I understand how we do things today, a wrecked ship and it's cargo don't change owners, but the salvors are legally entitled to a financial reward, backed by a marine court and, perhaps more practically, insurance. The key point is there are protections for both the original owners and the salvagers; it's never purely finders-keepers, unless you're going criminal. You don't have to copy this exactly; you might decide to do it the other way around, with space salvagers gaining title from an Admiralty court after a partial payment to the owners (possibly necessitating an auction if the salvors don't have ready cash).
The broader takeaway is that whatever you decide on, in-setting lawyers
will have already thought this through. There's room for you to decide between an Imperial Admiralty court, or an Admiralty court backed by signatory local governments, or just a corporate board backed by the full weight of Big Insurance. But there will be some kind of system in place, that system will have protections for both ship owners and salvagers, and they will have have some kind of plan for making it stick. If nothing else, there shouldn't be any clean title and registry without appearing before whatever form of Admiralty court you decide on.