Most Member National Authorities (MNA's) of ISAF - in other words - the Sailing Federations /Associations of each country, have found a place on the WWW. Some of them publish material for local Judges, Race Officers and Umpires. The big countries - like USA, Canada etc - have an extensive program, with many levels of skill and training, certification etc. They also publish quit a lot of material on the rules. In the form of a newsletter or appeals-decisions. When you are studying to become an International Judge this provides a great source of material. One of my favorites is the Canadian Yachting Association. They have an extensive site with a great deal to offer. I've made a file with excerpts from the CYA Judges newsletters with some very interesting rules questions. File: Excerpts CYA Judges Newsletter. The complete newsletters are also worth reading. Go to: http://www.sailing.ca/racing/officials/ and scroll down a bit.
Please do remember that the information is sometimes primarily focusing on national issues - i.e. Canadian prescriptions etc. Nevertheless you can - for study purposes - learn a great deal on the Racing Rules of Sailing.