The implication in the article is that the casinos weren't directly involved in the money laundering. Those who were perpetrating it brought the money into the

The implication in the article is that the casinos weren't directly involved in the money laundering. Those who were perpetrating it brought the money into the casinos (ie bought chips with "dirty" money), engaged in otherwise legitimate looking behavior at the casinos, and then cashed out the chips for cash. Apparently, the loop on this was tight enough not to fool investigators.