There is no permanent, official version of the full (either the 2009 original or the 2022 reboot) available for free download. The full games are paid titles available on digital storefronts like Steam and Battle.net .
However, you can access certain parts of the Modern Warfare II (2022) experience for free through specific modes and periodic events. Call of Duty® Store | Modern Warfare II Call of Duty: Modern Warfare 2 PC Game Free Download