In Sophocles' Antigone, what evidence is there that Creon's decree is either just or unjust?
Sophocles argues through the character Tiresias, the soothsayer, that punishing the dead is foolish. In other words, Creon has made his decree forbidding Polynices' burial out of revenge because he sees Polynices as a traitor for battling his brother Eteocles for the crown, which led to the deaths of both brothers. Tiresias points out that avenging oneself on the dead is foolish. As he states it:
Obstinacy brings the charge of stupidity. Yield to the dead, don't kick a fallen man! What prowess does it take to kill one already dead? (1031-34)
In addition to Creon's decree being foolish as it seeks revenge on the dead, it is also argued that his decree is also blasphemous. Tiresias argues that the dead belong to the gods and that Creon will be punished for holding back Polynices' "unhappy, unburied, unholy corpse ... from the gods below" (1078-80). Even Antigone herself argues that the gods' laws are higher than Creon's laws and that he has no right to try and override them, as we see in her lines:
I would never think your pronouncements had such strength that, being mortal, they could override the unwritten, ever-lasting prescriptions of the gods. (462-465)
Hence, we see that Sophocles argues all throughout the play that Creon's law was indeed unjust, foolish, and irreverent. In addition, Creon is chastised for his stubbornness.