On Sunday, T-Mobile will begin slowing down cellular data for some of its customers who violate the company's terms and conditions.

Under the new policy, unlimited data users who use their phones to upload "continuous" Web cam videos or engage in peer-to-peer filesharing will be throttled after a series of warnings.

"A very small number of our customers are misusing their Simple Choice Unlimited data service in violation of their rate plan and terms and conditions by bypassing the default tethering feature or engaging in peer-to-peer filesharing," the company told the Post. "In order to protect all T-Mobile customers, we will be reaching out to these people to educate them on our terms and conditions of service, but if the misuse continues, they could have their data speeds reduced for the remainder of their billing cycle."

A leaked internal memo obtained by Tmo News explains that users who violate the rule will have a notice appended to their account, and will receive warnings before being penalized for their behavior.

Streaming video and file sharing can quickly eat up a great deal of bandwidth, constraining the network for other users. For similar reasons, Verizon recently announced a plan to throttle the most voracious LTE users on unlimited plans on its network. The move has drawn scrutiny from federal regulators who believe the reason for targeting unlimited data users — as opposed to customers on metered plans — is motivated by a desire to increase revenues.

In response, Verizon has pointed to the fact that all wireless carriers engage in some form of data throttling as part of their "reasonable network management." The Federal Communications Commission has rejected that argument, saying that just because "all the kids do it" is not an excuse to discriminate among different types of customers.

T-Mobile's reported policy diverges from Verizon's in one key respect: The throttling would be triggered only when customers have violated the company's terms and conditions. That's a much more legalistic argument than the one Verizon appears to be making, which is that it simply wants to maintain a smooth network experience for everybody -- a type of moral/ethical argument.

Whether T-Mobile's approach will run afoul of the FCC is unclear; the agency declined to comment.