what is the law of the club, and what dose buck learn from it ?

 Buck learns that to survive he must fight..... that people and dogs are savages, and that love, respect, and personal feeling made one a fool.

t was all well enough in the Southland, under the law of love and fellowship, to respect private property and personal feelings; but in the Northland, under the law of club and fang, whoso took such things into account was a fool, and in so far as he observed them he would fail to prosper.