Traveller 'verse: the empire

The empire sounds kind of sinister...

But really it's more 'distant.' It's the paradigm. Hereditary families called nobles look after the somewhat time-consuming and arcane world of interstellar relations...after all, who else has time to sit for 3 months on a starship just to go to a meeting?

The empire itself regulates and protects interstellar trade. Everything else resides in the jurisdiction of its member worlds, which can have any government they like: It has a very, very few rules:

• No non-imperial warships with jump drives (there are some ways to skirt around this, megacorporations have heavily armed route protector cruisers, there are interstellar mercenary corporations...but internal warfare can't interfere with commerce at large without the Empire intervening.
• All tarriffs to member worlds must be lower than those to non-member worlds by 50%; and tarriffs can't exceed 5%.
• No use of nuclear NCB weapons;
• No slavery.

The empire can of course claim jurisdiction in cases of interstellar commerce, and has its own court system. But there is no appeal to the imperial level: a judgement on a planetary level is final, it's final.

The empire supports itself through something like a 0.5% revenue tarriff on interstellar trade, which adds up to ALOT of money, and a fairly large military, though ground forces are not organized on a federal level except in times of war (think civil-war-era USA)

The imperial Credit is the usual medium of exchange in interstellar trade, though member worlds are allowed to issue their own currency, and even make it the only legal form of exchange onworld. Rate-fixing is not a problem, because it's illegal.

So there you have it.