

Is it a subscription based store, like a Costco?
If so, you signed up for the cart checks. The only thing you can do is not shop there.
If not, once you pay for it, it’s yours, and they have no legal right to touch it or check it unless you give them permission.
All you have to do is kindly say “no thank you” and keep walking. If they stop you, they’re violating other laws.
If they suspect you of theft, they can calls the cops. Otherwise, they must let you pass.
The corpos and cops know the laws and, as such, your rights. It’s time we all know them, too, so we can put them (corpos and cops) all in their place on the ground.

They can, but if they ban you for not allowing them to check, that’s illegal, and you can sue. If they ban you for theft, they need the cops to prove it.
Keep in mind, you must be kind when you refuse. A nice smile and kind “no thank you” is enough. If you’re combative, they can ban you for that. If they’re dicks that ban for the sake of banning, fuck em