The pilot (PIC or SIC) is responsible for ensuring that they meet Part 67 "fitness for flight" and it's a shared responsibility under Part 121 in terms of required rest in between duty periods.

I think the "I have to commute because I can't afford to live in domicile" argument is DOA when set against the regulations. A pilot's responsibility is clearly defined, although the definition exists in an untenable work environment for many.

Also consider that most airline pilots are not true "at will employees" because they are covered under a CBA. A pilot can quit for any reason, or no reason at all - but the reverse may not be true for the employer wanting to terminate a covered pilot. Airlines will likly exploit this and suggest "if it's so bad, why do you do it?"

When the latest pilot rest issue comes to head, it's going to be easy for airline lawyers to quote chapter and verse of the existing regs and claim them adequate (ie. no additional expense or scheduling burden). I think the focus will again shift to the pilot, and force commuting pilot's hands to wheather the glamour of an airline career is worth it.

I hope I'm wrong.