A single internal Department of Justice email could be the smoking-gun document in the Operation Fast and Furious scandal — if it turns out to contain what congressional investigators have said it does.

The document would establish that wiretap application documents show senior DOJ officials knew about and approved the gunwalking tactic in Fast and Furious. This is the opposite of what Attorney General Eric Holder and House oversight committee ranking Democratic member Rep. Elijah Cummings have claimed.

It appears that email would also prove senior DOJ officials, likely including Holder himself, knew in March 2011 that a Feb. 4, 2011 letter from the DOJ to Iowa Republican Sen. Chuck Grassley falsely denied guns were permitted to “walk” into Mexico. The DOJ allowed that false letter to stand for nine more months, only withdrawing it in December 2011.

During the June 24 broadcast of Fox News Sunday, House oversight committee chairman Rep. Darrell Issa cited the email as a “good example” of a specific document his committee knows Holder is hiding from Congress.

“The ATF director, Kenneth Melson, sent an e-mail. And he had said to us in sworn testimony that, in fact, he had concerns,” Issa said. “And we want to see that e-mail because that’s an example where he was saying, if we believe his sworn testimony, that guns walked. And he said it shortly after February 4, and [on] July 4. When he told us that, we began asking for that document.”

But the details of it surfaced first when Grassley mentioned it for the first time publicly during a June 12 Senate Judiciary Committee hearing where Holder was testifying.

“He [Melson] immediately sent an email warning others, ‘back off the letter to Sen. Grassley in light of the information in the affidavits,’” Grassley explained.

Ken Melson, now the former acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, purportedly sent that email to several DOJ leaders in March 2011. According to Grassley, Melson wrote that he had reviewed the wiretap applications — the same documents Cummings and Holder claim do not show senior DOJ officials knew of or approved gunwalking tactics in Fast and Furious.

“ATF Acting Director Kenneth Melson described reading those same wiretap affidavits in March of last year,” Grassley told Holder during the Senate hearing. “He said he was alarmed that the information in the affidavits contradicted the public denial to Congress.”

It appears Republican congressional investigators first learned of the Melson email’s existence on July 4, 2011, when Melson chose to give a lengthy deposition on Fast and Furious without DOJ and ATF lawyers present. Grassley told Holder during the Senate hearing that congressional investigators first requested that the DOJ provide Congress with that email during July 2011, shortly after Melson made his then-secret trip across town to Capitol Hill.

The wiretap documents themselves are under federal court seal, leaving Grassley and Issa to tussle with Holder and Cumming about what they might show. Issa has said a whistleblower provided copies to his committee.

Holder has declined to ask the federal judge who sealed them to unseal them. The March 2011 Melson email, then, may be the only legal way — without violating a court order — to document the agreement of some senior Obama administration members with Issa’s and Grassley’s characterizations of the documents.

Melson’s email could also prove that although senior DOJ officials knew in March 2011 that the Feb. 4, 2011 letter was false, they chose to continue misleading Congress with gunwalking denials for several months.

“We need to see it [the email] to corroborate his testimony,” Grassley said during the June 12 hearing. “But the Department is withholding that email along with every other document after Feb. 4, 2011.”

Grassley pressed Holder on the question of how DOJ had the authority to withhold Melson’s email from Congress, a full week before President Obama indicated that he would invoke executive privilege to shield requested documents. At that time, Holder claimed the Melson email would not be protected by executive privilege.

“On what legal ground are you withholding that email?” He asked. “The president can’t claim executive privilege to withhold that email, is that correct?”

“Well, let me just say this: We have reached out to Chairman Issa to work our way through these issues,” Holder filibustered. “We have had sporadic contacts and we are prepared to make – I am prepared to make – compromises with regard to the documents that can be made available. There is a basis for withholding these documents if they deal with the deliberative …”

“But not on executive privilege?” Grassley interrupted.

“No,” Holder responded.

Holder spokeswoman Tracy Schmaler wouldn’t answer when The Daily Caller asked her if the DOJ was planning to provide the Melson email to Congress.

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