Under the revived WIPO Broadcast Treaty, broadcasters would have the right to stop you from using public domain and CC-licensed video footage as you choose, effectively giving them a new copyright over material simply by sending it out over the air.
The rules would also prohibit breaking DRM that was used to lock up public domain and CC-licensed broadcasts, and would let them stop fair use.
Copyright is supposed to protect creators, for limited times. Under these rules, broadcasters who did no creative labor would be able to trump the actual license conditions of the creators, and to assume the mantle of creator, merely for electromagnetically modulating other peoples' creative works through a wholly automated process.
The latest draft of the treaty also attempts to control post-fixation uses of broadcast signals—in other words, to provide broadcasters with rights to control uses of content that has been recorded from a broadcast.
The problems with this should be obvious. Since these post-fixation rules would apply regardless of whether the content was in the public domain or whether a "fair use" argument applies, it could impact the work of journalists, archivists, and creators who could otherwise legally gain access to source content through broadcasts.
The Danger of New Post-Fixation Rights in the WIPO Broadcasting Treaty