Therefore Frank Schleck clearly infringed Article 1.3.033 of UCI's technical regulation, which states that “it is forbidden to wear non-essential items of clothing or items designed to influence the performances of a rider such as reducing air resistence or modifying the body of the rider”. 

But the Luxembourg cyclist was certainly not the first to break the rules: also Tony Martin, winner of this year's Paris-Nice thanks to the victory in the time trial stage, was wearing a fairing on his chest similar to that of Frank Schleck (see pictures 29, 46, 80 and 88 on Cyclingnews.com and the pics of Fotoreporter Sirotti on Roadcycling.com). 

An embarrassed Frank Schleck and his Team gave some pretty risible excuses: the "camelback" mentioned by the rider didn't even have the tube to drink from, nor any strap to hold and sustain the weight of the water, as the bag was likely filled with air anyway... 
Such aerodynamic solutions come from wind tunnel studies, and being very visible, they spread rather quickly through the peloton. 

In any case, the riders and their teams are not the real culprits. 
The UCI commissioners allowed these riders to start: either they were not paying attention, or they don't know the Regulations or, worse, they simply closed their eyes.