I am not sure if Sun Cruz comes under US law since they operate out of the country.

Gambling states issue chips under state laws that comply with federal law that allows chips to be used in gaming.
Under this law, the chips ALWAYS belong to the casino. You can NOT own them.

If Sun Cruz complys with said laws, then they would have the right to knock on your door and say "Gimmee my chips."

That said:
They won't!
And:
They can not stop you from selling them on ebay. Ebay would laugh at them and send them one of those non-sensical emails, if they tried.