As for the proposition that imperial law doesn’t exist, only imperial edicts, it seems to me that this argument is one of semantics. Granted, we think of law as being legitimized by consensual government, but in any sort of non-consensual government, edicts and laws are essentially the same thing. As for naval officers rending legal judgment, I’d think that this would be delegated to lesser nobles. Part of being a noble in a campaign might be to sit as judge in whatever local cases fall into imperial jurisdiction. As for the edicts themselves, I’d like to see a list if anyone has one.

Generally speaking, however, I’d say that Imperial Law focuses on the relationships between the member states (the worlds) moreso than the relationships between individuals. Hence, the crimes that it covers would tend to be crimes that are committed not by individuals so much as governments and megacorps.

As for what these crimes might be, here’s a short list:

1. Treason

2. Failure to pay taxes

3. Illegal aggressions against or occupations of other recognized states

4. WMD proliferation

5. Genocide

6. Chattel slavery

7. Giving aid to interstellar pirates, terrorists, etc.

As for the hierarchy of nobles, I don’t really mind it, although I recognize that it’s probably not all that realistic. Nonetheless, in a universe where political authority is very top-down, it seems arguable that such a hierarchy could be maintained.

One of the things I have a problem with in the OTU is all the landless nobles wandering around. In my view, every noble of baronial rank and above should have authority over a fief, and that fief should produce income and pay taxes. Hence, barons and above would be unlikely to stray too far from home.

As for baronets, knights, and squires, I could envision them being the sub-landholding class of nobles that roams the stars doing the dirty work of the rest of the nobility. Baronets might be largely administrators and judges. Knights might be commanders of the police and mid-sized naval vessels. Squires could act as intermediaries or be tasked with special missions. The titles of all non-landed nobles would probably be provisional. Landed nobles too might lose their title though mismanagement. I was thinking about calling such stripped nobles knaves, although its arguable as to whether such a derogatory term would be used in an official capacity.

As for the offspring of nobles who are in the line of succession, I’ve usually termed them princes or princesses, regardless of the rank which they might inherit. This may be partly due to the fact that many an imperial baron would be, in effect, the governor of a planet or a large section thereof (or, at least, the imperial overseer of such a territory), and hence might be locally called a king, or Kaiser, or tsar, or whatever title is common to that culture.

Come to think of it, given the importance of titles in a “government of men”, prince/princess may be just the most generic term for someone who is in the line of succession. I could envision official titles conveying information on how close the person is to holding actual power. "I am Tertice Eneri, third in line to the barony of Foobar. This is my sister, Secundess Eleni. Princess Riga couldn’t attend, but she sends her regards."

Granted, this sort of uniformity would be unlikely given the sheer size of the Imperium, but it would be desirable in the sense that titles would actually mean something. If you were dealing with a baron, you’d know you’re dealing with someone who has actual power somewhere, not just somebody who was awarded or inherited an honorary title but has potentially fallen on hard times and is now collecting welfare. To do otherwise, I think, would be to undermine the nobility by accepting a system where their titles are rendered essentially meaningless by handing them out to every Tom, Dick, and Eneri, which, unfortunately, seems to be the case with the OTU. But that’s just my Cr2.