Last week, Verizon announced that it was extending its “Network Optimization” policy , which throttles speeds for the top 5% of data users, to include LTE data for the first time. This move didn’t sit well with the few remaining Verizon customers with “unlimited” data plans, nor did it thrill FCC Chair Tom Wheeler (who is apparently in a letter-writing mood this week ).

“I am deeply troubled by your July 25, 2014 announcement that Verizon Wireless intends to slow down some customers’ data speeds on your 4G LTE network,” writes the Chair in his letter [PDF] to Verizon Wireless CEO Daniel “fetch me a flaggon of” Mead.

Unlike some data-throttling plans that automatically slow the speeds for those users who gobble up gigabytes because they love watching House of Cards on their phones a little too much, Verizon’s Network Optimization only throttles data when those heavy users are currently connected to a cell site experiencing high demand.

The nation’s largest wireless provider justifies the continued bending of the meaning of “unlimited” by saying that Optimization is needed for “network management.”

The FCC already has a definition of what defines reasonable network management practices, clarifying that they must be “appropriate and tailored to achieving a legitimate network management purpose, taking into account the particular network architecture and technology of the broadband Internet access service.”

In his letter to Mead, Wheeler reminds VZW that “‘Reasonable network management’ concerns the technical management of your network; it is not a loophole designed to enhance your revenue streams.”

The Chair says it is “disturbing… that Verizon Wireless would base its ‘network management’ on distinctions among its customers’ data plans, rather than on network architecture or technology.”

He gives examples of legitimate network manager purposes, like “ensuring network security and integrity… by addressing traffic that is harmful to the network; addressing traffic that is unwanted by end users… and reducing or mitigating the effects of congestion on the network.”

But, writes Wheeler, “I know of no past Commission statement that would treat as ‘reasonable network management’ a decision to slow traffic to a user who has paid, after all, for ‘unlimited’ service.”

“What is your rationale for treating customers differently based on the type of data plan to which they subscribe, rather than network architecture or technological factors?” he asks Mead, adding that he wants the CEO to provide an explanation for Verizon’s statement that, “If you’re on an unlimited data plan and are concerned that you are in the top 5% of data users, you can switch to a usage-based data plan as customers on usage-based plans are not impacted.”

Verizon’s answers to these questions, and how the FCC responds, could have a huge impact on the wireless industry as Verizon is not the only carrier who throttles data on users with so-called “unlimited” plans.