I thought on this also, and I suppose in my "rule" to adhere by I would have to choose a time in human history. I'd likely choose a time from year 0-1000 but would need to research and get input from folks smarter than I before choosing the time that rule would be implemented.

Of course, it only bans colonization. This is specifically the act of taking over lands from those who are indigenous to said lands, usually by force. If the governments of two lands what to trade or sell their lands in agreement without force, this would not be illegal.

I'm certain humans would still find a way to be horrible in some other new fun way.

Fell asleep thinking of a question similar last night. No colonialism. Colonizing other lands outside of your own established borders would be forbidden.

How different the world would be.

I can't cants the seventh inning stretch in American baseball. It's like, hold on everybody we have to stop the game and be patriotic to the spaghetti monster real quick with this song or we can't continue the game.

At least half of my high school never stood for this, I'm actually a little shocked so many would "stand out". 50% of my homeroom in any given year did not stand or cross our hearts or whatever. We had more atheists than religious people, more alt kids than preps. Assuming this is why.