The US government plans give law enforcement agencies wider powers to intercept internet communications.
Law enforcement and national security services have requested access to a number of types of online communication that have previously proved problematic, including social networking sites, encrypted email services such as those used by BlackBerry handsets, and peer-to-peer messaging services like Skype.
The Obama administration intends to present a bill to Congress next year that would require all providers of such services to ensure that they were technically capable of complying with a 'wiretap' or surveillance order, providing access to communications and unscrambling any encrypted information.
Talking to the New York Times, James X Dempsey, vice president of the campaign group Center for Democracy and Technology, said the proposal had "huge implications" for Internet freedom, and threatened its decentralised design.
"They are really asking for the authority to redesign services that take advantage of the unique, and now pervasive, architecture of the Internet," said Dempsey. "They basically want to turn back the clock and make Internet services function the way that the telephone system used to function."
Officials from the Federal Bureau of Investigations, the Justice Department, the National Security Agency and others have been meeting with White House staff to thrash out the proposals, which they insist are necessary if they are to counter the global threat of terrorism.
No agreement has yet been reached on key elements such as deciding exactly who is defined as a communications service provider - but the law will aim to regulate providers that fell outside the scope of earlier legislation.
The existing US Communications Assistance for Law Enforcement Act 1994 allows federal investigators to tap into communications at points such as network switches - but if those communications are encrypted, security services require the additional cooperation of the communications service provider to hand over an unscrambled version.
Many of these providers are not subject to the 1994 Act, so law enforcement officials are required to serve individual wiretap orders to get this information. The new law would oblige providers to hand over unencrypted versions of the data on an ongoing basis.
But the law doesn't stop there. It could affect the way such services are designed in the future. Peer-to-peer messaging services are difficult to tap because they don't travel through a central hub. The chief suspect in the failed Times Square bomb plot in May, Faisal Shahzad, was discovered to have been communicating via a service with no built-in interception capacity. The new legislation could require all networks to be designed in a way that allows intercepts.
Officials are said to seeking powers to intercept data stored on servers based abroad, such as those BlackBerry maker Reasearch In Motion uses to provide secure email services. Such providers will have to open a US office from which intercepts can be performed - and will be required to hand over unscrambled versions of requested communications.
RIM has found itself in hot water with a number of governments around the world over the last three months, with authorities in India and the Gulf States threatening to ban certain BlackBerry services unless the company handed over unencrypted data.
Critics warn that the proposed US legislation may be used as a blueprint for highly restrictive measures elsewhere in the world.