Developers will be required to disclose if their game uses kernel anti-cheat. This applies to both new games and existing games. Non-kernel anti-cheat is encouraged to be disclosed as well, but it’s only mandatory for developers to declare if they’re using kernel anti-cheat for the time being.
It’s worth mentioning that many games use kernel anti-cheat on windows, but only use user space anti-cheat on Steam Deck and Linux.
It should only be applicable to new sales. Old sales should function the same as before.