First it was the drug testing, now it's the swim caps.
"Front and back of our caps...," he wrote on Twitter. "We used to be able to have front and back side with flags but for some reason there are rules that tell us we cant do that anymore? Smh gotta love an organizing committee telling us we can't do that anymore..."
"Smh," by the way, is an abbreviation for "shaking my head." He then posted a picture of the old style flag cap next to the new plain ones.
Phelps was Tweeting from Vichy, France, where he and his team are practicing before heading to London for the start of the games on July 28.