Verizon has begun blocking customers who use workarounds to tether their mobile devices without a Verizon-approved tethering plan, Boy Genius Report reported Monday. The move comes days after AT&T announced it will start forcing tetherers onto approved tethering plans, and just as the debate ramps up on whether curtailing tethering apps violates certain rules Verizon agreed to when it licensed a chunk of 700MHz spectrum for 4G use.

BGR noted that one of its writers, who uses a rooted Motorola Droid X and an unauthorized app to tether other devices, recently found that trying to navigate the Web on tethered devices redirected her to a Verizon Wireless page detailing rates for the company's authorized hotspot plans. This is perhaps a more measured response to tethering than AT&T, where customers must choose between discontinuing their tethering ways or getting forcibly moved to a more expensive tethering plan.

Customers who use tethering apps that don't have carrier-approved tethering plans have recently been a point of debate in net neutrality policy. Both AT&T and Verizon have forbidden such unapproved tethering in their customer agreements for years now, but the advocacy group Free Press recently complained to the FCC that blocking tethering apps "curtails, restrains, and interferes" with the ability of customers to use apps of their choice, something that would violate the open access rules Verizon agreed to when it bought a won the 700MHz "C block" of spectrum at auction.

Verizon responded to the Free Press complaint, stating that since it is not blocking tethering entirely, but rather charging for the privilege of using it, the company would be doing nothing wrong in preventing customers from circumventing these charges. The company says that C-block rules "permit nondiscriminatory tiered or usage-based pricing plans that require customers with greater capabilities or higher usage patterns to pay a higher fee." Tetherers use vastly more data than the average mobile user, according to Verizon, and therefore should be charged more.

In the statement, Verizon goes on to say that it should be uncontroversial to halt apps that allow customers to avoid paying more for a service they use more of, and "any other conclusion would be nonsensical."

Free Press fired back on Monday, saying that "terms of service agreements do not supersede federal regulations"—if the regulations say Verizon can't discriminate on a per-app basis, the fact that customer agreements prohibit tethering is immaterial when it comes to tethering apps. "When users buy wireless data service—whether capped or unlimited—they should be free to decide how they use that data," Free Press says, and it accuses Verizon of charging customers twice for the same data with their tethering plans.

In statements to Ars, Verizon talks around the actual blocking of applications, at best saying that it has only "suggested" that third-party app stores not host them. But Free Press insists that Verizon is violating the C-block conditions even if merely "requesting" companies like Google not host those apps, and that allowing Verizon's behavior could set a dangerous precedent for carriers to block any mobile apps they choose.

The FCC has agreed to examine the issue; in the meantime, though, tethering app users not subscribed to the right data plan will be out of luck.