Rugby was first codified in the early 1800s by a bunch of lawyers who had played a similar game at Rugby School in England. This is why rugby has "Laws" and soccer has "rules".
The Laws are based on two principles: Fair competition and continuity of play. Although the Laws can be daunting to learn and apply some knowledge of the Laws can make the game quite easy to understand.
Click on the Laws button and visit the International Rugby Board.