What Measure Is a Non-Human?: Averted to varying degrees (and, obviously, in the naïve sense, completely averted since there are no humans at all). The standard view, in the Associated Worlds, is that described in the Universal Accord on Sophont Rights: anything that thinks and has volition (i.e., is a sophont) is a person, and is entitled to all the rights associated therewith, and is exactly equal in the exercise thereof to every other sophont.
The Empire plays this very straight, and does, indeed, include all sophonts, including non-native aliens (and, yes, the starfish kind, and even the not-yet-understood), uplifts, neogens, artificial intelligences whether embodied or infomorph, uploaded minds, clones, forks, etc., etc. without distinction. Anything and everything that thinks.
They also go further in extending limited, but still extensive rights to the merely prosophont, including more limited artificial intelligences and higher animals. (The Empire is noted, in these cases, for eschewing “animal cruelty” laws in favor of simply broadly applying their existing laws where they fit. In the Empire, you are expected to swerve your vehicle to avoid hitting animals of this class – and, y’know, not do tuna fishing the way we do tuna fishing, or eat octopodes, or go whaling at all – and should you, say, shoot someone’s non-uplifted dog without equivalent self-defense justification to that which you’d need to shoot a full sophont, you will be charged with corpicide and/or cognicide, and will suffer the full criminal penalties, including – if deemed malicious and/or sadistic – potentially being shoved into the fires of purification and purged out of the universe.
(And, yes, that we don’t do this, and, in fact, behave in the manner listed on the trope’s [since deleted] Real Life page are among the many reasons that they’d consider us to be playing Humans Are Bastards very straight indeed.)
Some would argue that they also go farther and extend at least some rights to inanimate objects – that, however, is not a matter of law, that’s just a matter of Blue and Orange Morality and that going around willfully damaging and/or destroying things really gets people’s negentropic hackles up. Which then in turn, courtesy of this opinion being generally held, the reputation network, and the unlimited freedom of non-association, leads to being absolutely crucified in the Court of Public Opinion, and finding it very difficult to maintain any kind of reasonable lifestyle.
The civilized mode of the Associated Worlds follows this at least as far as sophonts are concerned, taking the broadest view there in law, although some private bigotries persist, as ever, and interpretation of some of those rights may locally vary (the Empire has long since had to recognize that it’s not going to be able to ram its views about government by the unanimous consent of the governed down everyone’s throat just yet).
Some of the less civilized parts (and, indeed, the arguably-superpower Voniensa Republic, which as an Expy of the Star Trek Federation replicates its noxious attitudes towards AIs, transsophonts, and property rights) carve out their own exceptions with regard to particular members of the list, which is where all those AI-slaver civilizations that produced the Silicate Tree, anti-upload ephemeralists, anti-uplift naturalists, etc., etc., come in. And, of course, a few nasty areas don’t really apply these principles at all; the Equality Concord, for example, doesn’t recognize any sophont rights other than The Right To Serve The People With All Your Heart And Soul.
And finally, of course, there are all those backwater and uncontacted worlds that have never even heard of the Universal Accord, much less had a chance to sign it or not; travellers there are pretty much taking their chances. Some, pleasantly enough, are cosmopolitan planets in waiting, and sign on to a broad view as soon as they run into one. Others are nasty nests of nastier bigots who don’t recognize any personhood outside their own species, and for that matter, don’t even recognize the rights of plenty of people of their own species.
Like, say, Earth.