Yeah, no. They can try. People are sheep, and comply. Your stuff is your stuff, not their stuff any longer.
That’s all nonsense anyhow. The issue is these firms cannot handle “loss prevention” because they hire defective people and want to punish the innocent as a result. Try to stay focused on the issue, not minutiae
Yeah. No. Right back. That can and will work at Walmart. You are correct. It is your stuff and unless they have reason to believe it is stolen merchandise, all they can do is ask. They cannot force you to show them your receipt.
The rules you agree to for a membership at Sam's Club and Costco say they get to check. If you choose not to comply at these places, your membership can be revoked. In this case, it was Sam's Club. They can and will check your receipts against your goods.