I can't find any law anywhere which covers employee expenses while out of state. However, my wife is attending a conference in the Southeast and her employer is covering room and airfare only, and since the hotel happens to cover breakfast - then they are claiming breakfast is included.
Is there no law which obligates employers to cover meals while away from the state?

I can't find any law anywhere which covers employee expenses while out of state.

There are only a few states that require expenses to be paid for or reimbursed. California certainly does. I think Massachusetts does. Others don't, so far as I know.

If I was an employee and the employer required me to go on a trip that cost me money, even after filing taxes for unreimbursed business expenses, I would not be happy.

Agreed. Also, while CA requires that business related expenses be reimbursed, it does not require that the Per Diem method be used. I have worked for CA employers who required receipts for all expenses (no matter how small), put limits on how much could be spent and CA-DLSE was fine with that.

And like Scott, says there is no federal law on this, and he mentioned the only two states with any kind of state laws on business expense reimbursement.