This is also why FedEx has effectively killed the bill by telling the U.S. government that it would cancel its next large order of new Boeing aircraft if that law is passed.
Imagine how WalMart could make them soil themselves by announcing they would shutter every store at 6:01AM the morning after it passes?
A threat by Wal-Mart (or any other company, for that matter) to shut itself down entirely is not a very credible threat. A threat to shut down an individual store or group of stores, though, sure is.
And a threat to make dramatic reductions (in response to anticipated rising costs) of purchases from other major corporations is sometimes enough to scare the sh!t out of even the most radical leftist in Congress.