It seems as though Call of Duty: Modern Warfare 2 players will be required to connect a phone number to their Battle.net account before playing the game.
"Call of Duty: Modern Warfare 2, newly created Overwatch 2 accounts, and newly created Call of Duty: Modern Warfare accounts, require that you add a phone number to your Battle.net account."
"Limiting the number of free accounts that a single person can create helps keep players accountable for their actions and, in turn, reduces toxicity and cheating and ensures a positive community experience for all players."
While Blizzard recently backtracked on the SMS Protect system for Overwatch 2, it remains to be seen whether Modern Warfare 2 will lift the restriction as well. And even Blizzard didn't backtrack completely. New players or those who have not played since June 9, 2021, still have to provide a phone number to play the game.
And, should these players live in a household that shares the same phone number or use a prepaid or VOIP number, well, they won't be able to play the game. Basically, it's a "sorry you can't afford a contract, let us know when you get one" sort of deal.
Hopefully, Activision will remove the restriction so those new to the series can hop into the game.