The Laws is Plato's last and longest dialogue. The question asked at the beginning is not "What is law?" as one would expect- that is the question of the Minos. The kick-off question is rather, "Who is given the credit for laying down your laws?"
It is generally agreed that Plato wrote this dialogue as an old man, having failed in his effort in Syracuse on the island of Sicily to guide a tyrant's rule, instead having been thrown in prison. These events are alluded to in the Seventh Letter.
Unlike most of Plato's dialogues, Socrates does not appear in the Laws. This is fitting because the dialogue takes place on the island of Crete, and Socrates never appears outside of Athens in Plato's writings, except in the Phaedrus, where he is just outside the city's walls. Instead of Socrates we have the Athenian Stranger (in Greek, 'xenos') and two other old men, an ordinary Spartan citizen (Megillos) and a Cretan politician and lawgiver (Kleinias) from Knossos.
The Athenian Stranger, who is much like Socrates but whose name is never given, joins the other two on their religious pilgrimage to the cave of Zeus. The entire dialogue takes place during this journey, which mimics the action of Minos, who is said by the Cretans to have made their ancient laws, who walked this path every nine years in order to receive instruction from Zeus on lawgiving. It is also said to be the longest day of the year, allowing for a densely-packed twelve chapters.
By the end of the third chapter Kleinias announces that he has in fact been given the charge of laying down laws for a new Cretan colony, and that he would like the Stranger's assistance. The rest of the dialogue proceeds with the three old men, walking towards the cave and making laws for this new city.
The questions of the Laws are without limit:
The dialogue uses primarily the Athenian and Spartan (Lacedaemonian) law systems as background for pinpointing a choice of laws, which the speakers imagine as a more or less coherent set for the new city they are talking about.
The Laws is similar to and yet in opposition to the Republic. It is similar in that both dialogues concern the making of a city in speech, but different in that the one city is ideal, and the other a real, practical city. The city of the laws is described as "second best," whereas the beautiful city of the Republic is the best possible city. The city of the Laws differs in its allowance of private property and private families, and in the very existence of written laws, from the city of the Republic, with its communistic property-system, possession of women in common, and absence of written law. Also, whereas the Republic is a dialogue between Socrates and many young men (Cephalus goes to bed early, after attending to his boring old sacrifices), the Laws is a discussion among old men, where children are not allowed and there is always a pretence of piety and ritualism. All in all, while the Laws is more similar to the Republic than any other dialogue, they are so different that the Laws needs to be considered in its own right, as Plato's most serious and comprehensive contribution to political philosophy.
It has the sense of a writer trying to get everything into his last work, yet its structure is comparable to the Symposium in its beauty and grace.
Plato was not the only Ancient Greek author writing about the law systems of his day, and making comparisons between the Athenian and the Lacedaemonian/Spartan laws. Notably, following text of another Socrates pupil has survived: Xenophon, The Polity of the Athenians and the Lacedaemonians.
Some centuries later also Plutarch would devote attention to the topic of Ancient Greek law systems, e.g. in his Life of Lykurgus. Lykurgus (or: Lycurgus) was the legendary law-giver of the Lacedaemonians. Plutarch compares Lycurgus (and his Spartan laws) to the law system Numa Pompilius introduced in Rome around 700 BC.
Both Xenophon and Plutarch are stark admirers of the Spartan system, showing less reserve than Plato in expressing that admiration.