AT&T

Late last year, the FTC filed a lawsuit against AT&T, stating that the carrier was throttling data for users on unlimited plans, a practice that has allegedly been going on since 2011. AT&T is now looking to file a motion to dismiss the lawsuit by invoking the Tier II "common carrier" clause, which exempts the carrier from FTC's jurisdiction and places it under the purview of the FCC.

Here's what AT&T states:

AT&T plainly qualifies as a 'common carrier' for purposes of Section 5 because it provides mobile voice services subject to common-carrier regulation under Title II of the Communications Act. The fact that AT&T's mobile data services are not regulated as common-carrier services under the Communications Act is irrelevant. The text, structure, history, and purpose of Section 5 leave no doubt that its common-carrier exemption turns on an entity's 'status as a common carrier subject to [an Act to regulate commerce],' not its 'activities subject to regulation under that Act.'

The FTC cannot rewrite the statute to expand its own jurisdiction.

The carrier already settled an $105 million lawsuit with the FTC in October over mobile cramming, in which it charged customers "millions of dollars in unauthorized third-party subscriptions and premium text messaging services."

Even if AT&T manages to successfully get the FTC suit dismissed, it will have to deal with the FCC, who is also looking to sue the carrier for the same reasons. As noted by AT&T in its motion to dismiss the FTC lawsuit:

The FCC's Enforcement Bureau is now actively considering whether to issue a Notice of Apparent Liability against AT&T alleging that AT&T's public disclosures of its MBR [maximum bit rate] program failed to satisfy the FCC's transparency rule and proposing statutory forfeitures. The FTC seeks to litigate the very same issues in an inappropriate parallel proceeding.

AT&T said that while mobile data was not a common carrier service, it does face regulations under Title III of the Communications Act and Section 706 of the Telecommunications Act.

Source: AT&T (Scribd), Ars Technica