Sega's publishing rights for Alpha Protocol have now expired, resulting in the game's removal from Steam.
Eurogamer noticed that the Steam page for Obsidian Entertainment's spy-themed RPG featured the following statement from Sega, which published the game in May 2010.
"Notice: At the request of the publisher, Alpha Protocol is no longer available for sale on Steam."
A spokesperson for Sega clarified that the withdrawal of Alpha Protocol was due to the expiration of the company's publishing rights, putting the game back in the hands of Obsidian Entertainment.