Costco by my house has removed there signs here in colorado.
I was refused entry into the Marquette Wal Mart a couple of years ago because of openly carrying my sidearm. The manager's reason was.... she couldn't allow any unsecured guns in the store. Never mind she had no idea how many concealed guns were being carried in the store by other customers at that precise moment... my sidearm in the open was reason enough for her to refuse entry for me.
And she was well within her private property rights.. and the trespass laws... to do that.
Wal-mart as a whole is pretty solid with regard to allowing citizens to exercise their rights.
"A few well placed shots with a .22LR is a lot better than a bunch of solid misses with a .44 mag!" Glock Armorer, NRA Chief RSO, Pistol, Rifle, Shotgun, Muzzleloading Rifle, Muzzleloading Shotgun, and Home Firearm Safety Training Counselor
What Glockfan said. Contact corporate if harassed.