The first generation of Internet controls consisted largely of building firewalls at key Internet gateways; China's famous “Great Firewall of China” is one of the first national Internet filtering systems.
As you can see in the video, the officers asked the attendees to remove the posters, after the refusal the security guards bundled the poster up and took it away.
The book is a global project from the OpenNet Initiative (ONI), a collaboration of the Citizen Lab at the University of Toronto's Munk Centre for International Studies, Harvard's Berkman Center for Internet and Society, and the SecDev Group.
Jonathan Zittrain blogged about the phrase and the incident on his small article “The sentence the UN doesn't want you to see” 
Its presence on a poster advertising the OpenNet Initiative’s academic book Access Controlled was enough to deem it prohibited by UN security forces at the Internet Governance Forum, who are shown in these videos removing the poster from the room over the objections of OpenNet colleagues Ron Deibert and Rafal Rohozinski.
The United Nations  is an international organization founded in 1945 after the Second World War by 51 countries committed to maintaining international peace and security, developing friendly relations among nations and promoting social progress, better living standards and human rights. The work of the United Nations with its 192 members reaches every corner of the globe.
The Internet Governance Forum mandate is to discuss  public policy issues related to key elements of Internet governance in order to foster the sustainability, robustness, security, stability and development of the Internet. The IGF Secretariat's activities are funded through extra-budgetary contributions paid into a multi-donor Trust Fund  administered by the United Nations Department of Economic and Social Affairs (UNDESA).
The topics discussed in the book “Access Controlled” are Internet filtering, censorship of Web content, and online surveillance and its increasing in scale, scope, and sophistication around the world, a worthy discussion during the IGF2009.
Below is the statement made by Ronald Deibert and Rafal Rohozinski after the removal of “Access Controlled” poster by UN Security services at IGF09. The Video has been recorded by Global Voices Advocacy Director, Sami Ben Gharbia .