Too simplistic a question. There are many unconsidered variables that would be fodder in EASA-land for yet more regulation.
We can go 10 flying hours multi -crew, and if that's required the odd day to make it work then so be it. The next day won't have 10.
Are you living at home and driving to work each day -coming home after a long day to a cranky wife, broken hot water heater and rotten kids- not much rest to prepare for the next day. Or, are you equal time touring, 5star hotel, drop your underwear on the floor and the maid picks it up?
Is it a two hour straight run, no weather, to the rig on sheepskin seats, aircon and no suits? Or a day full of 10 min shuttles on pitching heaving decks?
Is the patronage obligated copilot trying to kill you every time he has the controls?
Any good chief pilot/mgr weighs all these factors to manage fatigue over a run period, no regulations required. Still, offshore is easy work compared to 1200 hrs/year of production/precision long lining, and lots of 10 hour+ days there, every day.