The new Call of Duty update makes teamkillers hurt themselves

Call of Duty's new update across both Black Ops - Cold War and Warzone has implemented a change to League Play: Friendly fire damage will now hurt the attacker after their 2nd teamkill, and teamkillers will be kicked after two additional attempts at teamkilling. Here's the full patch note: "Friendly fire will now convert to ricochet damage after the 2nd teamkill and return damage to the attacker. Players will be kicked after 2 additional attempted teamkills after that." The update has been fairly well-received by Call of Duty league players on social media.

A similar system is used to great effect in Rainbow Six Siege, which implemented it in 2019. It turns up occasional false positives, but I'd wager its done more harm  than good. Griefing isn't as common on competitive ladders as on open matches, but it's a brutal thing when someone does decide to go rogue.

The full patch also includes several bugfixes for both multiplayer and zombies mode, mostly having to do with positioning and UI bugs. You can read the full Call of Duty February 13 2021 patch notes on Treyarch's website.