"The source also claims that there'd be no license transfer of any sort, which means that any purchases made on Stadia would effectively be nullified as the service closes down." There clearly needs to be a law to make such things illegal. I've refused to take the discount on digital Switch games since Nintendo has clearly shown they are willing to shut down old servers and tell you to just buy your games again. But…
The problem is that there really isn't a way to legislate it. The content is tied to the service (either the platform service like the Switch, or the game service itself), and if the servers aren't running, you're done. No backup is going to help you. And there's piracy. I do not see any governments creating legislating to force publishers (or platform (e.g. Steam) or console manufacturers) to remove anti-piracy measures.