People here will definitely agree that it is in violation of the NAP, as evidenced by their objection to even gambling.
The argument is whether a contract which doesn’t involve property can be enforced. My position is that any contract, if people want to stick to it, can be laced with property.
Then again, I have not read much on contract theory, so I cannot say for sure, but hope to learn from this discussion.
Imo any contract can be considered a service, hence enforceable.