They can do that for games using steam drm. Even for games using custom drm they can let it remain on your pc if you have already downloaded it, it’s not their duty to remove games from your pc even if devs pull games from steam. Whether custom drm games continue to work or not will depend on if they phone home are not.

Anyone can be sued obviously, but there will be no ashes, they aren’t random Joes to be afraid of legal trolls.