Contract and society are not just creations of the mind ~ they exist, per se, with or without cerebral counseling.
If you see that, you must see that the United States Constitution explicitly recognizes the pre-existing right of "the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures... (emphasis added).
That's the right some people believe Wal Mart violates, even if they don't put it that way.