Have you heard the joke about the plumber who, when asked to solve a plumbing problem, charged the client $200 for simply hitting the pipe really hard with his wrench - $1 for the actual hitting, and $199 for knowing where and how to hit it? read more
To know every law by heart you would need to know every law at the federal level and every single state law, and every single local law, as well as reading about every single legal case (or at least the ones in their state, because what happens in other states has no precedence for them). read more
But even in civil law countries, most bodies of law are so large that no one can know everything--lawyers therefore typically attempt to become experts in particular areas, not generalists. To use the American example, just about all American law students study criminal law, civil procedure, contracts, torts, property, and Constitutional law. read more
Many people think that a judge knows all the laws. That they’re presented with issues, and like the oracle, pronounce the law, correctly, every time, from on up high. Unfortunately, our society, and the laws that govern us, are too complicated for any one person to know it all. read more