Laws of the Game
1. The authentic version of “Laws of the Game” is published annually by FIFA, the highest governing body for the world-wide game we call soccer. FIFA is a non-profit organization and updates the Laws annually through an arm of their organization called IFAB.
The “Laws of the Game 2020-2021” are found here.
2. National and provincial organizations (like Soccer Canada and Ontario Soccer) distribute authoritative versions of these Laws and other important memorandum on the various forms of the game. These rules and memoranda are located here.
For example, a simplified version of the game using fewer players (9 v 11) is explained here.
3. In Ontario, there is a specially modified version of the game for younger players. It is called the "Small Sided Game". The authoritative version of this game is found here.
A useful memorandum on the “retreat line” rule used in the small sided game is located here.