What are the rules of the jungle in The Jungle Book?

It may seem strange to have rules in the jungle. After all, the expression "the law of the jungle" has come to be synonymous with people being able to do what they want, whenever they want. But, as Mowgli learns from growing up in a wolf pack, there are indeed a number of rules in operation in the jungle to make sure that all the many animals who live there can do so without too much animosity. They are as follows:

• The strength of the wolf lies in the pack, and the strength of the pack in the wolf. This means that all members of a pack must work together for the common good.
• Wash daily, drink deeply, but not too deep. The night is for hunting, the day is for sleeping.
• A jackal may follow a tiger to find food (i.e., scavenge some scraps), but once a wolf is fully grown and has all his whiskers, he must get his own food.
• Keep the peace with the lords of the jungle, such as the tiger, the panther, and the bear. Also make sure not to mock Hathi the Silent—a large Indian elephant—or the boar in his lair.
• If your pack should meet another pack in the jungle, lie down and wait until the leaders of each pack have spoken. This is a way of preventing fights breaking out between rival wolf packs.
• If a fight should break out with a wolf from another pack, you must fight him yourself well away from the other pack members. This is to ensure that a full-scale war doesn't break out, which would diminish the size of the pack.

Mowgli learns the Law of the Jungle from Baloo, who knows all of the laws and teaches them to Mowgli, at least in part because Mowgli is an eager student, whereas the wolves typically learn only the rules that apply the most to them. Laws are mentioned or defined occasionally, such as not killing anyone at a watering hole when a "water truce" is declared. Fear is implied to be the only "law" that applies equally to all animals.

In "The Law of the Jungle", a number of rules are laid out, although we are told that there are "hundreds and hundreds" more, plus these are only the rules that are followed by or pertain to wolves. 

Most of the laws are guidelines for living, and how one is meant to interact with other wolves and other animals so as to minimize conflict. A few of the laws do provide a sort of overall authority; for example, the word of the Head Wolf is law in all judgments that are not immediately obvious, and the "haunch and the hump" of the law, i.e. its core, is to obey. Most emphatically, the law states that one must never kill man, i.e. a human.

What are the Laws of the Jungle in The Jungle Book?

The Laws of the Jungle are found throughout the text of The Jungle Book. Readers learn them alongside Mowgli or through discussions between the wolves.

Now this is the Law of the Jungle—as old and as true as the sky;
And the Wolf that shall keep it may prosper, but the wolf that shall break it must die.

The first Law of the Jungle readers learn about is spoken by Father Wolf. He states that Shere Khan has no right to change his hunting grounds on a whim. Shere Khan is supposed to warn the other creatures first, as his presence will scare away other prey, forcing the hunters to go hungry.

By the Law of the Jungle he has no right to change his quarters without due warning.

The second law readers learn is that the animals of the jungle are forbidden to eat humans, except in order to teach their young to hunt and kill. Even then, the hunting of "Man" must be done outside of one's usual hunting grounds.

The Law of the Jungle, which never orders anything without a reason, forbids every beast to eat Man except when he is killing to show his children how to kill, and then he must hunt outside the hunting grounds of his pack or tribe.

The third law states that a wolf may remove himself from the pack when he marries; however, the couple must bring their cubs, when old enough to walk, before the Pack Council so that "the other wolves may identify them" and understand they are of the same tribe.

The Law of the Jungle also states that a disputed cub must be spoken for by two members of the pack that are not its father or mother. Baloo the bear and Bagheera the panther both speak for Mowgli.

Other laws state that one must not kill for pleasure; one must keep peace with the Lords of the Jungle (tigers, bears, panthers, boars, etc.); and one's dispute with another must be handled alone, without pack involvement, as the pack would then be "diminished by war."

What are examples of "The Law of the Jungle" in The Jungle Book?

In The Jungle Book, the "Law of the Jungle" is a set of rules by which the civilized animals conduct their lives and business. Since the animals are more intelligent than in real life, they are able to codify and create a set of rules to govern their behavior; the rules are based in pragmatism and instinct, since some of the animals are not as civilized, and wild nature dictates a level of response to attack, rather than reasoned argument or discourse. A good example is the prohibition against killing Men:

The Law... forbids every beast to eat Man except when he is killing... man-killing means, sooner or later, the arrival of white men on elephants, with guns...

As shown, this Law is bad in pragmatism, since indiscriminate killing of Men means large-scale retribution. In the end, animals will fall to Man's guns, so it is better to not incite Man with random killings.

Another example is punishment; to the animals, there is no sense in grudges if the Law is broken. When Bagheera's honor is damaged by Mowgli's actions, the law dictates that Mowgli be punished, despite his regret; however, this punishment acts to wipe the record clean, and there is no resentment.

One of the beauties of Jungle Law is that punishment settles all scored. There is no nagging afterward.
(Kipling, The Jungle Book, Google Books)

Other Laws are explained in the text through action and by Baloo, who serves as teacher; each Law acts on the story, dictating how Mowgli grows and learns to live with the animals according to their rules and instincts. Mowgli's own instincts are of Man, and so he thinks differently, but he understands the need to abide by the Law, despite his own instincts to the contrary.