Sunfish & others: If it's legal it's OK.
Driving down the motorway at + 50mph is legal; in the fog it's legal. After the crash it is considered Bl&*)y stupid, but it was legal. The crime was negligent driving. Does the same exist for pilots? Legal does NOT make it correct!!!!! The escape clause is do not fly if you do not consider yourself fit, but risk your livelyhood. I would expect that more than 50% of pilots who have to fly 5 earlies are knackered after 3, How many do the correct thing and cry off the 5th?