"The Law of the Jungle" is an expression that means "every man for himself", "anything goes", "might makes right", "survival of the strongest", "survival of the fittest", "kill or be killed", "dog eat dog" and "eat or be eaten".
In the novel The Jungle Book, Rudyard Kipling uses the term to describe an actual law code used by wolves and other animals in the jungles of India.
"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.As the creeper that girdles the tree-trunk, the Law runneth forward and back;
For the strength of the Pack is the Wolf, and the strength of the Wolf is the Pack."
Phil Jackson: Sacred Hoops