A federal judge has ordered that Facebook should get access to what it calls the “smoking gun” in the strange saga of a New Yorker who claims to own more than half of the social networking giant based on a contract that Facebook says is a forgery.

Both parties agree that Mark Zuckerberg signed a contract in 2003 with Paul Ceglia, the would-be heir-apparent to Facebook, to do some freelance programming work. But in 2010, Ceglia filed suit, produced a copy of the contract that also included a $1000 investment in “The Page Book” entitling him to half of Facebook. Facebook charges that Ceglia, who has a checkered past, forged a page of the contract.

Now Facebook will get to see the contract that Ceglia sent to his lawyer in a series of e-mails in 2003. Facebook described these as the “authentic contract” that were smoking guns proving fraud. Ceglia’s current set of lawyers tried to keep those e-mails out of the case, citing attorney-client privilege.

But on Thursday, U.S. Magistrate Judge Leslie Foschio overruled that designation and said the four e-mails, along with dozens of other pieces of evidence designated as “confidential” by Ceglia, had to be turned over to Facebook’s lawyers by 10 a.m. Wednesday morning.

Foschio’s ruling wasn’t published until Sunday. The full ruling reveals that Foschio decided that just because the e-mails were sent by Ceglia to his then-lawyer, that does not make them protected.

“Because the e-mail merely transmits another document — the contract — to an attorney, it neither seeks confidential legal advice nor constitutes a confidential communication relating to such advice,” Foschio ruled. “Specifically, the contract, already signed by Zuckerberg, by definition cannot be considered as a confidential communication…”

If indeed, the original contract differs significantly from the one produced in 2010, when Ceglia said he discovered the existence of Facebook and remembered that he’d been the first investor, the suit will likely end.

That, in turn, will likely stamp “The End” on the long-running legal saga over Facebook’s founding. That drama included a now-settled suit with three Harvard classmates — including the now infamous Winklevoss twins — made famous in the 2010 Hollywood hit, “The Social Network.”

Facebook is valued above $80 billion, and is widely expected to hold an IPO sometime in 2011.