Both the Platonic and Aristophanic Socrates expose the difference between justice and law through situational ironies.
In Plato's Apology, Socrates is condemned to death by the Athenian democracy for the crimes of asebeia (impiety) and corrupting the youth. Although Socrates argues that he was not guilty of either crime, he actually does not fully answer the charges. When asked to name a lesser penalty, he mocks the system by proposing a reward. Later, in Crito, he explains his views that it is just for him to obey the laws whether the law is good or bad. Combined with the argument from Gorgias that it is worse to commit than to suffer injustice, one can deduce that Plato attributed to Socrates the position that human laws were imperfect, but that justice for the individual involved obedience to existing laws -- and that since the laws affect only external circumstances rather than the soul, that they are only minimally relevant to the ideal justice which occurs in the individual soul.
Aristophanes has a more conventional view of justice in Clouds in which the Old Logos sees good laws and consonant with justice and the New Logos, Socratics, and sophists articulate the position that laws are inherently conventional, having nothing to do with any form of natural justice.
The position of Socrates in Clouds is probably closer to that of the historic Protagoras than that of the historic Socrates.