I don’t think it should be regulated either. I still think F1 is a little bit overregulated anyway.
I think a driver’s own moral sense should be enough to decide the issue: it is always the case of being a true professional or not. Those who will not give it their all will not be and they will have to live with that – that they were not true racing drivers for certain moments, to paraphrase Ayrton a bit.
Michael Schumacher letting Vettel through in the dying stages of the Brazilian GP seems to gain more and more importance for me in this respect. He was my childhood idol, I was a Schumacher fan during this ‘first career’. I somehow kind of overlooked his controversial moves, probably due to not being as sensitive to my own principles earlier as I am now, but he could not got away with that one. He ruined a lot of his legacy for me by not putting up any fight. It was in stark contrast with the Michael Schumacher who bowed out of the sport in 2006 at the very same track, who fighted tooth and nail to the last corner and never gave up not one place.
Note that I am fine with team mates letting each other through as well. I am a Ferrari fan and I accepted their controversial, cruel racing philosophy a long time ago: the team comes first.