kerni experimental gismu

x1 (state/event/fact) is fair/just/righteous to x2 according to x3

According to x3, the way x2 is treated in x1 is just (it is "as things should be"). See also pajni, sarxe, vrude, vudypai, nutli, pairnu'i. (Many of those words deal with some judge acting "fairly" or "justly" in some matter, which kerni does not. In fact, a "to'e kerni" (unfair) situation is not necessarily the result of evil, may be considered unfair to all parties, and may be nobody's fault.)

In notes:

cadga
x1 (abstraction) should/(of right) ought to be true/happening under conditions/in the case of x2 being true/happening, as believed by/by standard/under consideration of x3. If the world were proper/correct/just/ruled perfectly and strictly according to x3 and if x2 were true, then x1 would be true as well.
kamkerni
x1 is the fairness/justice of situation x2 toward x3 according to x4.
tolkerni
x1 (state/event/fact) is unfair/unjust to x2 according to x3.