EA said the changes that paved the way for Crysis 2's Steam return were made outside of the publisher, instead adopted by developer Crytek.
"Changes made by Crytek to Crysis 2: Maximum Edition have brought the game back into compliance with Steam’s terms of service," said an EA rep.
Its never been mentioned why EA's titles were pulled from the service, but it has been generally assumed the addition of in-game stores in its games broke Steam policy.
Valve boss Gabe Newell said at the time "a whole complicated set of issues” were the reason why EA titles were pulled from the service. Several titles published by EA Partners, like Crysis 2, are already on Steam, such as Kingdoms of Amalur: Reckoning, Shank 2 and Warp.
A Crysis sequel, Crysis 3, launches next spring for PC, Xbox 360 and PS3 through EAP.