The ATF agent who blew the whistle on Operation Fast and Furious has been denied permission to write a book on the botched anti-gun trafficking sting "because it would have a negative impact on morale," according to the very agency responsible for the scandal.

After first trying to stop the operation internally, ATF Agent John Dodson went to Congress and eventually the media following the death of Border Patrol Agent Brian Terry in December 2010. Two guns found at the murder scene were sold through the ATF operation.

Dodson's book, titled "The Unarmed Truth," provides the first inside account of how the federal government permitted and helped sell some 2,000 guns to Mexican drug cartels, despite evidence the guns killed innocent people.

Dodson, who is working with publisher Simon & Schuster, submitted his manuscript to the department for review, per federal rules. However, it was denied.

Greg Serres, an ATF ethics official, told Dodson that any of his supervisors at any level could disapprove outside employment "for any reason."

Serres' letter said: "This would have a negative impact on morale in the Phoenix Field Division and would have a detremental effect [sic] on our relationships with DEA and FBI."

The ATF said in a statement, though, that they did not actually block Dodson from publishing.

"ATF has not denied the publishing of a manuscript or an individual's 1st Amendment rights. We have denied Mr. Dodson outside employment which can be denied for any reason by a supervisor," the agency said. "While his supervisor stated morale and interagency issues for the denial, the fact remains no agent may profit financially from information gained through his federal employment while still an employee.

"This is not about 1st Amendment rights: this is about a current employee trying to profit financially from knowledge he has gained while currently employed as a special agent."

The national office of the American Civil Liberties Association is representing Dodson as he fights the decision. ACLU attorney Lee Rowland says the agency's restriction is overly broad.

Rather than provide a specific objection which would allow for a line-by-line redaction, ATF used a policy that "grants supervisors the discretion to censor critical speech simply because it annoys or embarrasses the ATF," Rowland wrote in a letter delivered Monday.

"Given the national importance of both the Fast and Furious operation and ATF practices more broadly, ATF faces an extremely high burden in demonstrating that its interests outweigh Agent Dodson's right to speak -- and the public's right to hear -- his views about Operation Fast and Furious," she explained.

First Amendment rights are especially strong when the speech affected deals with public policy, Rowland said, requiring the government to meet a very high bar. Precisely because Dodson's views differ dramatically from those of his supervisors, his "thoughts and opinions" should not be censored, Rowland said.

Fox News legal analyst Lis Wiehl said the federal code prohibiting employees from outside compensation from speeches and writing could pose a significant problem for Dodson.

"He is still an agent with the ATF and the ATF has very strict restrictions," Wiehl said. "You can't receive compensation for outside employment, including writing a book, without permission."

On the other hand, Wiehl said, the ATF may have overplayed its hand by saying it can deny publication "for any reason."

"What kind of hubris is that when a whistle-blower wants to go on public record -- the First Amendment says he should be able to go forward," she said. "The ATF created their own embarrassment, maybe its own negligence -- that agent Dodson had the courage to reveal. And now he is being punished for that."

The ACLU argues ATF rules are "constitutionally inadequate (and result) in impermissible censorship of the speech of a public employee."

Dodson says "The Unarmed Truth" will come out in January, with or without the ATF's permission.