The translation of "law" is misleading. The word is torah, and in this context it does not mean a code of rules written in a book, like a book of law. That aspect is found in the word "commandments" or "statutes," which means written, in this case, on stone. The word is literally "engraved." "Law" is teaching or instruction, suggesting a relationship that exists because an instructor is teaching a pupil.
When God says, "they have despised the law," in reality they have rejected Him, the Instructor. In effect, He says, "The relationship has been broken and now you are breaking My commandments," showing that it is a cause and effect process. Just in case they missed the point, He illustrates what He meant from examples out of society.
John W. Ritenbaugh
Guard the Truth!