If you were to create a game/competition.
It is you who has sole right to make the rules, being the creator of the game.
You could stipulate that the contestants could make the rules up as they whent, rules that might help the free flow of the game or cause the game to come to a halt , but then you have already made a rule(there is no rules).
You could create rules, then the contestants being free willed could breake the rules because it suited them, you as the games creator at this point could
A:disqualify all cheating contestants,
B:turn a blind eye to the cheating
C: create a new rule that over writes the first rules
So the game will work as long as your rules are followed and every thing here would be well within your rite as the creator because it is your game.
This system works with games created by a collective group as long as the governing body is in agreement with each other, but when one dissagrees with the rules and has their own ideas the a slightly different game is invented

Atheism is different to this.
Atheism says there is no ultimate governing body over this game we call life, we are all playing our own "game" making up our own rules as we go along. If this were the case we would have no right to critisize or dictate the rules to another, for their "game" is there own created by them selfs. If someone violates the rules of your game, that is they are living by their own rules, in the eyes of the atheist it cannot be immoral.
Most atheists though cannot live like this, because they cannot live without at least some of there own rules being followed. and like wise society cannot exist if there werent rules handed down from a higher authority, namely God
For it is only the creator who has the exclusive right to impose rules. It would be immoral for a man or a society to impose rules on a nother man unless they were handed down from the creator of this world.