IN A SANCTIONED TOURNAMENT AM I REQUIRED TO WARM-UP?

Yes, you are required to warm-up . . . for your opponent as well as for the process of changing the balls at proper intervals.

Interesting question.

I'm trying to figure out why you wouldn't want to gain 5 minutes worth of information on your opponent. I found the rule. Rule 3 of the 45 page "The Code" states that:

"Warm up is not practice. A player should provide the opponent a 5-minute warm-up. If a player refused to warm up the opponent, the player forfeits the right to a warm-up. Some players confuse warm-up and practice. Each player should make a special effort to hit shots directly to the opponent. (If partners want to warm up each other while their opponents are warming up, they may do so.)"

So no. You are not required to and you can refuse your warm-up. But your opponent still gets the opportunity to warm-up with the new balls you'll be playing with for 5 minutes...presumably with a warm-up partner of his choice. If he can't find anyone to warm up with, I guess neither of you gets a warm-up.