Patent Law is a very dynamic and complicated area of the law. These laws come from the laws and rules established by the USPTO, which is a division of the Department of Commerce. All the in's and out's of these laws and rules are explicitly written and described in the Manual of Patent Examining Procedure (MPEP). The MPEP is several thousand pages long and it references many of the official rules and laws established by the Patent and Trademark Office (PTO).
There are two sources for the laws and rules covered in the MPEP. The first is described in "United States Code Title 35 - Patents". The second source includes the rules described in the "Code of Federal Regulations - Patents, Trademarks and Copyrights". As far as patent law is concerned, you only need to worry about the Regulations covered in the Patent section of the code.
The MPEP includes all the relevant laws and rules you need to know in order to gain a patent. Within it, every angle of each law and rule is covered, in addition to the forms used to file a patent application. The writers of the MPEP have also made sure to fill it up with important court case citations used over the years to help establish the laws and rules of the Patent Office.
Now, we are not suggesting that any inventor (at least not one in his/her right mind) just sit down with the MPEP and begin reading. No way. You don't need to do that to yourself. That's what a patent attorney or agent is for. But you should be familiar with some of the rules and regulations of patents before you charge off to get one. You may want to check-out the Inventor's Patent Workshop, it's a home study course to get you moving in the right direction.