The lawsuit was filed by French consumer group UFC-Que Choisir against Steam four years ago, where they alleged that the platform practiced anti-consumer rights activities. Valve had attempted to argue that Steam is a subscription service, but the court rejected that notion claiming that Steam sells its games in perpetuity, and not part of a subscription package.
This means that legally, if you bought a game on Steam and decide you no longer want to play it, you can actually resell it like you would a physical copy of a game. Note that this ruling only applies to the EU due to a law in the region that allows all goods, including software, to be resold without permission of the maker or the original seller.
Before you get too excited about this, the ruling has yet to go into effect. Valve will be given three months to amend its terms of service, but at the same time, they are also planning on appealing the ruling which could delay it coming into effect. In a statement made to Polygon, a Valve spokesperson said, “We disagree with the decision of the Paris Court of First Instance and will appeal it. The decision will have no effect on Steam while the case is on appeal.”