Having just watched the BBC Forum from Valencia, and their excellent breakdown of the Schumacher - DRS - Yellow Flag incident, there can be little doubt that the FIA will always have discretion to pick and choose what penalties they want to apply in any given situation. From Webber's onboard camera, it is clear as day that Schumi passed two yellow flag zones with the DRS open. If Mark, the trailing driver, was able to recognize the fact that DRS deployment was against the rules, then surely Michael should have known as well.
Furthermore, earlier in the show Ross Brawn claimed unequivocally that he had checked the data and Michael had closed his DRS 30m before the first yellow flag zone. No doubt they pitched this line to the stewards as well who would have been in perfect position to call this what it was, a flat-out lie.
It is clear to me that the FIA did not want to ruin a good story. And you know what, I don't even care. This incident had very little effect on Michael and Mark's race, and to have sent Schumacher back to P9 would have been a disgrace.
But this scenario proves the point that I and several others have harped upon for years. The FIA treats certain drivers differently, for one reason or another, in almost every case. And also that they are not bound by the very letter of the regulations. So when people say, "Oh well, it's in the rulebook", that argument doesn't carry any weight. It's been proven time and again that the FIA stewards are given the discretion to either apply a sanction to its fullest extent, or to simply ignore incidents that require a penalty by a strict reading of the regulations.