FINA has clarified its rules after a bit of a legal skirmish at the 2015 World Championships, officially announcing that Ryan Lochte‘s new twist on underwater kicking will be illegal in IM races moving forward.

The issue is with Lochte’s recent decision to do his underwater dolphin kicking on his back, even on freestyle races. It’s a technique Lochte and coach David Marsh came up with and debuted this summer.

Lochte is generally faster kicking on his back, and the decision helped him win his fourth consecutive world title in the 200 IM in Kazan.

Though the technique is perfectly legal in freestyle (and of course, backstroke), there was concern that it might not fly under FINA’s IM rules. The difference is that “freestyle” permits athletes to do basically any style of stroke, including any of the three other competitive strokes. But in an individual medley race specifically, the “freestyle” leg doesn’t allow for any of the three other competitive strokes to be used – that makes the race a full, four-stroke medley by preventing athletes from repeating one of the other strokes.

During the World Championships, there were rumblings that officials would define Lochte’s underwater kicks on his back as being “backstroke” under the legal definition of the rules, and that he would be disqualified for repeating a stroke in his 200 IM.

Lochte took a risk and swam his race with the new style anyway, and wasn’t disqualified. In a post-race interview, he said he hadn’t heard of a rule prohibiting underwater kicking on one’s back, but also predicted that the rule would be changed in the future.

Turns out, Lochte was right. Germany’s SwimSportNews reports today that FINA has clarified its IM rule, noting that Lochte’s technique will be considered illegal and disqualified in any future IM races.

FINA’s rationale is that “backstroke” is defined by a swimmer traveling lying on his or her back. So in underwater kicking on his back, Lochte is technically swimming backstroke for the first 15 meters of his freestyle lengths.

That’s still perfectly legal in freestyle races, but will no longer be allowed in IM races.

You can watch video of Lochte’s race here.