Mwa-ha-ha-ha-haaaaa! In Soviet Russia, the rule mentions you!!
I have broken the rule.
Everybody let me know if/when it is time for a hint. I will be here for a little while this morning, and then I have an all-day job I have to do.
I have broken the rule.
P.S. I suggest you look at all the violational posts, and see what they have in common.
I have broken the rule. Twice.
Just so you’ll know, I have been limiting my guesses so that others can have a chance to beat me to the answer. Somebody else needs a shot at Rule Maker.
Okay, look, it’s a certain letter combination within a certain common context.
I have broken the rule.
Ah, double letters, eh?
(Which means I broke the rule just then.)
Kuddos! 
No double letters within a prepositional phrase. (I love prepositions.)
Sorry, Zeldar, I didn’t mean to hog the thread.
Not to worry about “hogging” your thread. 
So do we have a new Rule Maker yet?
I believe the Prof. is in the barrel.
I shall attempt to puzzle your minds mightily. In that spirit, no clues, at least not initially.
I’ll try not to make a mess. With a stupid Guess.
You have not broken the rule.
No Haiku?
You have now broken the rule.
Every sentence must verb.
Must speak like a Wizard of Oz Munchkin.
Both of the above are in violation of the rule.
Maybe it’s something to do with capitalization within a sentence?
We have a variant of this type of game called “Magic [color] Door” and it’s played like this. Each round you have a doorkeeper and a bunch of petitioners who want to go through the magic door. The doorkeeper thinks up some rule, like “Only words with double vowels can go through my door” and the game begins. Sometimes you can whisper the rule to a second person and have a backup doorkeeper both to help everyone know you’re not playing a sucker game where the rule changes arbitrarily.
Doorkeeper “I have a Magic Green Door”
Questioner 1 - Can “Billy Ray Cyrus” go through the Magic Green Door?
Doorkeeper - “Billy Ray Cyrus” can not go through the Magic Green Door.
Questioner 2 - Can the “Magic Green Door” go through the Magic Green Door?
Doorkeeper - The “Magic Green Door” can go through the Magic Green Door. (depending on the age of the kids you may say “green door” yes, “magic” no.)
Questioner 3 - Can the “Magic Flute” go through the Magic Green Door?
Doorkeeper - The “Magic Flute” can not go through the Magic Green Door.
And on and on until the players figure out what the condition is, then a new doorkeeper is selected, a new magical colored door is created and the game continues. Good for road trips and campfires.
Enjoy,
Steven