I am trying to understand how baggage rules apply when flying two different carriers with different rules. It seems as though if one flight is domestic and one is int'l, then the int'l carrier's rules apply-- is that right?

However, I can't understand the rules for a purely domestic flight (or two international flights). Does it go by the first carrier, or is it the first carrier unless the second carrier "marketed" the flight (and does that mean more than simply sold you the ticket as a codeshare)?

I have tried poking around for this information but have only ended up confused. (I even saw one reference suggesting that baggage fees have to be the same for both legs of a roundtrip?)

Is there a wiki somewhere that explains how this works? Does it change airline to airline?

thanks