(CNN) -- A federal agent's attempt to write a book with an insider's account of "Operation Fast and Furious" is being blocked by superiors because it could have "a negative impact on morale," the American Civil Liberties Union said.
John Dodson, an agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives, was among several agents who claimed whistleblower status in order to provide information to Congress about the agency.
The controversial program allowed 2,000 guns to cross Arizona's border with Mexico beginning in 2009 with the intention of tracking them to criminal gangs.
Authorities lost track of hundreds of weapons that wound up in the hands of drug cartels and two guns wound up at the scene of a border agent's slaying the next year although it was not clear whether they factored in the death.
"Fast and Furious" was shut down in 2011 and was the subject of congressional hearings and investigations.
Dodson wrote a manuscript of his experience and prepared to seek a publisher, the ACLU said in a letter on Monday to the ATF. But his efforts were blocked by agency supervisors, who have oversight on any outside employment by agents, the ACLU said in the letter protesting the restriction.
ACLU lawyers said the ATF's actions on Dodson's publication request are an unconstitutional censorship of his freedom of speech.
"The reasons provided to Agent Dodson were predictions of 'a negative impact on morale' in his field division at Phoenix, and 'a detrimental effect [sic] on [ATF] relationships' with other agencies, the Drug Enforcement Administration and the Federal Bureau of Investigation, the ACLU said in the letter.
The lawyers said the ATF should revisit its decision and change its policies allowing supervisors to block the speech rights of employees for any reason.
The "Fast and Furious" operation gave rise to more than a year of political controversy for the Justice Department, and eventually to House Republicans to sanction Attorney General Eric Holder for contempt of Congress in a legal dispute over the White House's refusal to turn over documents.
Holder has said the tactics used in "Fast and Furious," which allowed weapons to fall into the hands of traffickers, should never have been allowed.
Dodson has claimed that Justice Department officials retaliated against him for providing testimony to Congress.
"Given the national attention to 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,'" the ACLU lawyers said in their letter which was written on Dodson's behalf.
In response, an ATF spokesman cited federal regulations that prohibit individuals from "writing about issues that arise from his or her duties as a special agent and profiting from his or her experiences while still acting in the special agent capacity."