Marriott wifi blocking

Saw this article: http://www.cnn.com/2014/10/03/travel/marriott-fcc-wi-fi-fine/ The interesting part: 'A federal investigation of the Gaylord Opryland Resort and Convention Center in Nashville found that Marriott employees had used "containment features of a Wi-Fi monitoring system" at the hotel to prevent people from accessing their own personal Wi-Fi networks.' I'm aware of how the illegal wifi blocking devices work, but any idea what legal hardware they were using to effectively keep their own wifi available but render everyone else's inaccessible? David