Marriott wifi blocking

[dhubbard at dino.hostasaurus.com (David Hubbard)]

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