Refers to the online multiplayer in the Call of Duty (usually Modern Warfare 1 and after) franchise. This scientific law states that any given player in any point in time is in his mind the optimal skill level:social life ratio, i.e anyone who is better than the player would be "loser who lives in his moms basement who has no life" and anyone worse is "such a f***in noob", who the player, respectively, pwned.
Player after losing a FFA match: "Wow that guy just went 30-1, probably some fat loser with no life."
Same player after beating somebody: "HAHAHA 3-45!!! you fkin NOOB i RAPED YOU!!!!"
Friend: "Wow man that's COD's Law for ya."