"We reinstate content when we receive a retraction from the party who originally submitted the notification,'' a spokeswoman for Google in Australia said. Google owns YouTube. Meanwhile, Professor Lessig's own legal action accuses the company of "extremist enforcement tactics" because it automatically issues take down notices whenever computers detect its songs, without taking fair use allowances into consideration. "I have the opportunity ... to challenge this particular attack. I am hopeful the precedent this case will set will help others avoid such a need to fight," Professor Lessig said recently. A spokeswoman for Mushroom Music, which owns Liberation, told Fairfax Media she had been advised by the company's lawyers not to comment. Liberation was yet to file a defence to Professor Lessig's complaint, which has been filed in the US District Court in Masschusetts. Professor Lessig argues Liberation Music "enforces its purported rights robotically" and made no effort to examine whether his alleged breach fell within the "fair use" limits of copyright law, which he believes it did.

During the 49-minute lecture on content collaboration, he demonstrates "call and response" communication through five examples of home-made videos of people dancing along to the hit song Lisztomania by French band Phoenix. Each clip lasts between 10 and 47 seconds and Professor Lessig spoke throughout the songs. YouTube received a take-down notice from Liberation on about June 30 and shut down public access. Professor Lessig issued a counter notice, but received a direct response from Liberation Music on July 8 threatening legal action against him in the District of Massachusetts, including a potential $US150,000 ($160,000) fine for copyright infringement. A letter from Liberation confirms the song was detected through automated scanning software. YouTube has a system called ContentID that scans videos for any audio or video used without permission. It has a library of 3 million "reference files" supplied by content owners. It is unclear why Liberation was taking action in the US, rather than the US rights holders, Glassnote Entertainment Group.

"Although Liberation Music's take down notice purported to claim that Professor Lessig's use of Lisztomania infringed Liberation Music's copyrights, this was a false statement. In fact, Liberation Music has implemented and enforced a policy of issuing take-down notices automatically whenever its content is used on YouTube," Professor Lessig's amended complaint states. It also argues that "Professor Lessig's illustrative use of the clips in question, particularly in the context of a public lecture about culture and the internet, is permitted under the fair use doctrine, and, therefore, does not infringe the defendant's copyright". The initial complaint was lodged on August 22, 2013. Professor Lessig has been supported by the San Francisco-based Electronic Frontier Foundation lobby group, which said legal action was taken to "[ask] a federal judge in Massachusetts to rule that the video is lawful fair use, to stop Liberation Music from making further legal threats, and to award damages". Daniel Nazer from EFF said the case would determine whether the increasing use of automated detection processes was stifling legitimate fair uses of copyrighted material, particularly in the United States. He said there had been a spike in the volume of automatically generated take-down notices in the past year, which was concerning "because fair use is fundamental to freedom of expression in the US".

A partner at King & Wood Mallesons in Australia, John Swinson, said this case would help determine if copyright owners were now "over-reaching or just enforcing their rights". "Computer-generated notices are a very blunt instrument and now we have a copyright expert taking on the computer to see whether the blunt instrument needs to be refined to have actual human involvement in the process," Mr Swinson said. The US has much broader "fair use" allowances than Australia. However, the Australian Law Reform Commission was considering the fair use exception as part of its current review of Australia's copyright and the digital economy laws. A copy of an automatically generated email sent by Liberation to Professor Lessig confirms it orders YouTube to automatically block any videos that uses its songs. Some record companies choose to take a small licence fee or let a song's popularity spread without restrictions. Loading

Liberation Music specialises in distributing Australian artists, but its subsidiary Liberator Music holds the rights for Phoenix in Australia and New Zealand. Liberator also owns the rights to Phoenix's back catalogue through a deal with the Glassnote Group. Update: An earlier version noted the video was still available in Australia. The story has been updated with comment from a Google spokeswoman confirming it restores access to videos if take down notices were retracted.