I think unnamed source they’re referring to is whoever the email was sent to. The article said it went out to “press (not including Kotaku)“.

Deny the site access to future content? No. That would be stupid. Ask that the site punish/remove the individual that broke the agreement? Sure. Request that the content be taken down until the time it was meant to be available to the public? Probably. Threaten legal action if the legally binding contract they entered…