Don't know if it's been stated; Wal-Marts policy on carrying guns into the store, at least in Pennsylvania, is that they comply with the state laws.
That has been made known through various phone calls to the corporation. They will not send it in text form though, as to keep it an open ended thing they can change at any moment.
Here's a link to an encounter a forum member had with Wal-Mart:
"Confronted at Walmart by security and asst manager"
*Read post on Page 4- Post #36 by Delerius.
Here's another link to another encounter at Wal-Mart:
"Kicked out of Wal*Mart Parkesburg (Chester County) for Open Carry"
*Read post on Page 4- Post #35 by iMoses14
*Read post on Page 6- Post #51 by iMoses14
*Read post on Page 7- Post #67 by iMoses14