In a blog post to the official Counter Strike website, Valve has announced that you will no longer be able to re-sell container keys that you purchase, and the keys will no longer be able to leave the purchasing account.
Starting today, CS:GO container keys purchased in-game can no longer leave the purchasing account. That is, they cannot be sold on the Steam Community Market or traded. Pre-existing CS:GO container keys are unaffected–those keys can still be sold on the Steam Community Market and traded. Why make this change? In the past, most key trades we observed were between legitimate customers. However, worldwide fraud networks have recently shifted to using CS:GO keys to liquidate their gains. At this point, nearly all key purchases that end up being traded or sold on the marketplace are believed to be fraud-sourced. As a result we have decided that newly purchased keys will not be tradeable or marketable.
Valve has advised that the reason for this change is a shift in worldwide fraud networks, which have begun to use CS: GO keys as a means to liquidate their gains. Surprisingly, they have said that at this point, “nearly all key purchases that end up being traded or sold on the marketplace are believed to be fraud-sourced.”
Valve has stated that they do not expect this change to affect the majority of the userbase, as most people buy their keys and then use them on the same account. While they acknowledge that the change will negatively impact some legitimate users, it is something that they need to do to stop the platform from being utilized to engage in fraudulent activities.
Companies like Valve need to take steps to combat fraud at every turn. Being seen to know about fraudulent activities, but take no steps to stop it, could lead to an awkward legal situation for any company. As such, it is understandable that they would take these steps.