What they're saying is: "we haven't called out any specific games, but we told steam if they can't prove a game is "lawful" well cut them off".

This effectively has a chilling effect because it means anything that could be illegal becomes toxic and risky for steam.

Its a way for Mastercard to dictate what can be sold without actually dictating what can be sold. Now the real issue is that at the end of the Mastercard is in a position where this matters and they can influence things. Should work just like cash and leave the government to decide what items are legal/illegal.