After two years in which rapidly changing technology helped swim apparel dominate the sport almost as much as Phelps, FINA banned controversial full-body suits, including some versions of Speedo's groundbreaking LZR Racer, which was designed with help from NASA.
Called "technological doping" by critics, these revolutionary swimsuits have been responsible for a rash of world records - 17 long-course marks in 2009 and more than 130 overall starting in 2008. In the wake, a Wild West atmosphere has consumed apparel manufacturers and swimmers trying to gain a competitive edge.
Yet, in turning back the clock to correct one problem, FINA's congress immediately exacerbated another on the eve of the championships, which start Sunday.
"There's going to be an issue no more," FINA executive director Cornel Marculescu said.
Not on the question of what to wear, perhaps, but what to say about records that have been set by swimmers wearing the high-tech suits. While the ban still must be approved by the FINA Bureau on Tuesday - all indications are that the vote will be a formality - it won't take effect until 2010.
Phelps, who holds five individual world records along with 14 Olympic gold medals, isn't worried. Of course, Speedo's most famous pitchman, who is here to compete in the worlds, also is one of the few stars of the sport who has not been tempted by each new generation of swimsuits.
"A swimsuit's a swimsuit," said Phelps, who Olympic gold medalist Gary Hall once said could roll out of bed "in cutoffs and break the world record."
"If you're ever going to compete at a high level and compete consistently, it's going to be because of the work you do in training. I've worked as hard as I can to get to where I am now, and I've put in countless hours.
"I like it," Phelps said of the ban. "I think it's going to be good."
Phelps wore the LZR Racer when he broke every one of the records in Beijing. But he owned those records before these suits were introduced.
Friday's news, though, set off a growing debate in the swimming community about how to define the record-setting performances since the sport went spinning out of control in early 2008, when the LZR Racer was introduced.
FINA's congress also stipulated the swimsuit coverage area must be between the waist and knees for men and not beyond the shoulders or below the knees for women. FINA also said suits may only be made from "textiles," though FINA officials said the definition of that would still have to be worked out.
USA Swimming's Mark Schubert has been known to favor an asterisk to define those record-setting swims. His boss, Chuck Wielgus, USA Swimming's executive director, does not.
"I don't think we want to do anything to tarnish the performances of the athletes of the past," Wielgus said. "Debate is human."
Speedo set the early pace last year, igniting pre-Olympic controversy over whether its swimsuits provided an unfair advantage.
Since the Beijing Olympics, though, the line has moved so far, so fast that even the slow-moving FINA decided to act.
Swimmers were wearing two, even three suits (now illegal) to get an edge while newer offerings from Italian swimsuit makers Arena and Jaked featured enhancing material, Arena with part-polyurethane and Jaked with all-polyurethane.
The high-tech suits are stitch-free, low-drag, super-light and help shed water along the surface of the suit.