Facebook's attempt to provide free access to a selection of websites in developing countries was dealt a blow today when India's telecom regulator banned arrangements that charge different amounts for access to different parts of the Internet. The move effectively prevents "zero-rating" schemes in which certain Web services count against data caps while others do not.

Facebook is partnering with mobile operators in various countries to offer "Free Basics," saying that the app provides "access to basic websites for free—like news, job postings, health and education information, and communication tools like Facebook." Any developer can try to get a website included, but Facebook imposes restrictions, including one that prevents high-bandwidth services like VoIP, video, and file transfers. In addition to Facebook, Free Basics includes AccuWeather, BBC News, Dictionary.com, ESPN, and other sites.

Critics say Free Basics violates net neutrality principles by prioritizing certain content, making it less likely that people will use websites not included in the app. The Telecom Regulatory Authority of India (TRAI) had temporarily banned Free Basics and today followed up with a new rule that prevents service providers from charging "discriminatory tariffs for data services on the basis of content." A discriminatory tariff under this rule includes free data applied only to certain websites.

The rule applies to telecom operators rather than Facebook, but it would prevent Facebook from partnering with mobile operators to offer apps that don't count against mobile data caps. Operators who violate the rule can be fined. One exception to the rule allows free access to emergency services.

Because most residents of India are not yet connected to the Internet, mobile operators should not be allowed to "shape the users' Internet experience," TRAI wrote. As more people gain Internet access, their usage should be "shaped only by the information made available through those select offerings," the agency said.

The rule doesn't prevent mobile operators from offering free data, as long as it can be used to access any content. "For instance, providing limited free data that enables a user to access the entire Internet is not prohibited," TRAI wrote.

Facebook is disappointed in the decision. "Our goal with Free Basics is to bring more people online with an open, nonexclusive and free platform," the company said, according to The New York Times. "While disappointed with the outcome, we will continue our efforts to eliminate barriers and give the unconnected an easier path to the Internet and the opportunities it brings."

Free Basics is available in a few dozen countries in Africa, the Asia-Pacific region, and Latin America, but the controversy extends beyond India. A recent report by the World Bank referred specifically to Free Basics and said that imposing data charges on some content but not others "would appear to be the antithesis of net neutrality and a distortion of markets."

Zero-rating is also controversial in the US, but so far the Federal Communications Commission hasn't taken any action to stop it.