They can't retroactively change DRM-Free install files sitting on your hard drive -- which is why it's important that you have control over your own shit rather than hoping for software stores to continue being benevolent. If you can't have the install media and use it any time you want, you're just renting.

It's also the reason why everyone should want local DRM-Free copies of their favorite songs and movies, because there's no guarantee that will continue being available. It's only a matter of time until the commissars start to realize that nobody is eating their slop and they start trying to pressure stores to stop providing the stuff people have already purchased, or to pressure streaming services to stop providing old movies or TV shows entirely since that's also going on.

But do you think steam doesn't let publishers change the games they publish? Because I got news for you... They can and they do.