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.
Add a clause to the contract between Steam and the developer requiring the dev to reimburse Steam for refunds due to post-sale changes (ie, from that specific ‘accept, decline, refund’ option). If the dev doesn’t pay the bill, Steam can use the breach of contract as leverage.