. . . gets a yellow card, apparently.
When I was playing soccer for a few years, I managed to make it through season after season and only collected one yellow card. I had the bad sense to get into an argument with the ref, during which I accused him of not knowing the Laws of the Game. He didn't take too kindly. Other than that, I managed to play a pretty clean game.
It's a good thing I didn't know about this particular provision, however:
A referee ordered a penalty to be retaken in a Sunday league football game when an opposition player broke wind as the ball was kicked.I always figured that the regulation of noxious, but non corporeal, bodily function during game play would be limited to something like cricket!
The Chorlton Villa player got a yellow card for the noise which was classed as 'unsporting behaviour'.