California Gov. Jerry Brown has signed into law a bill requiring companies to disclose whether they abide by Do Not Track provisions, a move that could build momentum for privacy protections that have stalled at the national level. On Friday, Brown signed AB 370, which requires internet companies that collect personally identifiable information to declare how they respond to Do Not Track requests. The idea is to pressure advertising networks like Google's AdSense and Facebook's FBX to be more transparent about how they track users' activity around the web.

Brown's signature comes as Do Not Track's future has been called into question at the national level. Earlier this month, a key online advertising industry group pulled out of discussions to create a national Do Not Track standard. The Digital Advertising Alliance, a trade group represents advertisers, said discussions with the World Wide Web Consortium (W3C) had "reached the end of [their] useful life." It was the latest in a series of setbacks that has seen the W3C miss multiple deadlines to craft a final proposal for the Federal Trade Commission and Congress to review.

Websites are free to ignore Do Not Track requests

Discussions with advertisers over the issue began in 2011. That's when Mozilla added a feature to Firefox letting users state that they did not want websites like Google, Facebook, and Twitter tracking their activity across the web so as to better target them for advertising. Microsoft, Apple, and Google later build similar features into their own browsers. But as San Francisco Chronicle columnist James Temple notes, websites are free to ignore Do Not Track requests — and have no obligation to even let users know they are being ignored.

AB 370 tries to change that by requiring companies to disclose in their privacy policies whether they honor Do Not Track requests. The idea is that to avoid being shamed, companies will begin stating officially that they will support Do Not Track. Officially, the law applies only to California — but because companies would be loath to craft state-by-state privacy policies, privacy advocates believe AB 370 will effectively become national law. And as Temple points out, if companies say they honor Do Not Track and then fail to do so, they are liable for punishment by the FTC.

If the bill is incremental, it's also a sign of how quickly Do Not Track has become a mainstream idea in policy circles. And if companies begin changing their privacy policies as a result of California's move, Do Not Track may finally become a standard with teeth.