Facebook's leaning on the Fourth Amendment, saying the government doesn't have the right to seize, look at, or keep private messages, shared media, or other communications of users without those people knowing.

BERLIN — The European Commission is planning a legal change next year that may prompt U.S. Web giants like Google and Facebook to rethink how they store and process consumer data, raising the prospect of a trans-Atlantic dispute over Internet privacy.

The European law gives individuals more control over the use of data they enter on free Web services, but it has not been revised since 1995, when the Internet was still in its infancy.

Facebook and Google have signed the Safe Harbor Agreement, a 2000 pact between the United States and the European Union under which U.S. signatories promise to handle the data of European citizens according to E.U. rules.

Facebook came under fire Thursday from privacy advocates who say that changes to its ad network mark an unprecedented expansion of its ability to collect users' personal data.

Facebook, of course, is no stranger to privacy criticism. In 2011, the company settled charges with the FTC over changes to its privacy policy

"It's true that everybody is doing all of this, and that's how the system works," Chester said. "But this is unprecedented. Given Facebook's scale, this is a dramatic expansion of its spying on users."

INTERNET PRIVACY is a murky, complicated issue full of conflicting interests, misinformation, innuendo and technology snafus.

Complicating matters further are criminals who break into Web sites, steal the information and use it for personal gain.

Advertising firms, who stand to gain as much as any from personal data collection, have absorbed the brunt of complaints from privacy critics