Who owns free spectrum?

The 2.4ghz frequency range has been set aside by the FCC for free use by devices like cordless phones and, of course, wireless networking devices. Recently, the University of Texas at Dallas informed residents that the use of 802.11b and 802.11g access points is prohibited in residential areas as it causes interference with the official university wireless service.

This has angered some resident students and brings up the interesting question of who can regulate "free" radio spectrum. News.com has some additional details here. They do seem to exempt 802.11a access points, as they use the 5.8ghz range, but with 11 channels available in the 2.4ghz range, isn't there enough room for everyone?