Simply putting games onto their existing Steam Community Market isn't going to be sufficient for compliance, much like how the Steam Wallet being the only option for a refund wouldn't have been sufficient back when that was before the courts.
Unfortunatly, it might be the only option in this case, as oppose to refunds. Allowing games on Steam to be sold second hand for real cash opens up a real possibility of money laundering, you could buy a game with dirty money, and sell it on multiple times, and clean the money. Then there are problems with overseas tax, and the price differences for Steam games, as well as regional limitations for certain games. There are things patched out in Germany that aren't the UK for example.
Trading digital goods for real money has a unique set of problems, which isn't faced by selling a physcial item.