There are only two rules:
1) In any exchange between participants of The Blawl Game, whichever says "BLAWL" first, wins that exchange. Note that, due to the nature of The Blawl Game, this is not accompanied by a loss for the other player; rather, the winner wins that exchange while the other player remains unaffected.
2) There must be a time period between exchanges to prevent Blawl spamming; this time period is defined as however long it takes for all members of the previous exchange to have stopped thinking about The Blawl Game.
Thus, if one participant were to win an initial Blawl exchange, and the two participants were to then have a several-minute conversation about other things, and the other participant were to then suddenly remember The Blawl Game, they could then slip "BLAWL" into the conversation and win the second exchange.
Person B: "Meh, I'm feeling a little blawl today."
Person A: "Happy Blawlday to you, happy Blawlday to you!"
Person A: "ROFB"
Person B: "Huh? Don't you mean ROFL?"
Person A: "Nope. ROFB: Rolling On The Floor Blawling."
Person A: "What does a giraffe have in common with a giant redwood?"
Person B: "Something about being tall?"
Person A: "Nope, actually they're both quite blawl."
Person A: *Reads this definition*
Person B: "Welcome to The Blawl Game."