Washington DC-based interest group Public Knowledge issued a brief press release this afternoon stating its displeasure with AT&T's decision to limit FaceTime over cellular — a new feature in iOS 6 — to subscribers choosing its new Mobile Share plans, arguing that the company is "violating the FCC's Open Internet rules." Here's the full statement from senior staff attorney John Bergmayer:

By blocking FaceTime for many of its customers, AT&T is violating the FCC's Open Internet rules. These rules state that mobile providers shall not 'block applications that compete with the provider's voice or video telephony services.' Although carriers are permitted to engage in 'reasonable network management,' there is no technical reason why one data plan should be able to access FaceTime, and another not.

'Over-the-top' communications services like FaceTime are a threat to carriers' revenue, but they should respond by competing with these services and not by engaging in discriminatory behavior.

As much as we'd all like for the FCC to take a comprehensive stand in favor of authentic, no-compromise net neutrality on wireless networks, the Open Internet rules that Public Knowledge is referring to are primarily geared toward landlines; in fact, the rule that the group is referring to is the only one that applies specifically to mobile. The Commission has been reluctant to take a hard line in wireless, where essentially all providers argue that there isn't enough bandwidth to treat traffic agnostically.

Does that mean AT&T is in the right? Absolutely not

The problem — and the one that we suspect AT&T will use to its advantage in the inevitable public policy debates over the coming weeks — is that you can easily argue FaceTime doesn't "compete with [AT&T's] voice or video telephony services." AT&T doesn't offer a native video calling service (even though it's been part of UMTS for nearly a decade in some parts of the world), and calling it a voice calling competitor is a hard sell, at least as long as Apple doesn't turn FaceTime into a full-on Skype foil.

Does that mean AT&T is in the right? Absolutely not — but Public Knowledge's well-intentioned argument may not hold up to scrutiny the way that the FCC's rules are currently written.