You did not buy them.
They are legally an IOU.
Can a casino rep knock on your door and say I'm cashing your chips? Legally Yes. Will he? Very doubtful

I will only address NV, but I believe the law is the same everywhere. The reg is written to comply with federal laws relating to printing alternative money.

The chips are always the property of the issuing casino. In effect they are an IOU. We can not sell them, you can not buy them. Can we stop you from leaving the casino with them? Yes. Will we? Not in 99.9% in the instance of cash value chips.