Wooper is right. It is a tax deduction, but only to the extent that your total miscellaneous itemized deductions exceed 2% of your Adjusted Gross Income. So if your income is $30,000 your out-of-pocket expenses would have to be at least $600.
There are no labor laws prohibiting this sort of thing. The basic reason for this is that everyone has to eat, whether they work or not.
No...You have to eat wherever you are, so if they don't feed you where you normally work, they don't have to feed you anywhere else.