Lawyers for a former State Department employee accused of leaking sensitive defense secrets are urging Attorney General Eric H. Holder Jr. to drop criminal charges, saying that the case might never have been pursued under current Justice Department guidelines on leak investigations.

Defense attorneys for former State Department arms expert Stephen J. Kim argue that the Department of Justice should abandon its case for multiple reasons — but largely because the new leak policy would have stopped investigators from obtaining some of the evidence they are now using to prosecute Kim.

Kim’s lawyers point out that the Justice Department’s new policy was crafted as a result of a public outcry over law enforcement tactics in Kim’s case — as well as in another investigation involving the collection of phone records of Associated Press journalists.

“It would be neither just nor reasonable for the Department to acknowledge that it was wrong, issue a policy to correct that wrong going forward, but still proceed to use the ill-gotten evidence against the defendant in the case in which the material was obtained,” Kim’s lawyers, led by Abbe D. Lowell, wrote to Holder in a Sept. 24 letter sent to House Judiciary Committee leaders that The Washington Post recently obtained.

The office of the U.S. Attorney for the District of Columbia, Ronald C. Machen Jr., responded on Holder’s behalf in early November, saying that the department has no intention of reassessing its prosecution or dismissing the case in light of the revised policies designed to protect press freedoms.

“This is an active criminal matter that should continue to move forward as we seek to hold your client responsible for his criminal conduct,” Machen’s criminal division chief Mary B. McCord wrote in the two-paragraph response.

Much of Kim’s defense rests on the argument that his alleged conversation with a Fox News reporter in 2009 appeared to cause little to no harm to national security and that his prosecution could end up causing more harm.

Under the amended policy, the Director of National Intelligence must certify to the Attorney General before the government seeks media-related records “the significance of the harm that could have been caused by the unauthorized disclosure” of national defense information.

Kim’s lawyers note that federal prosecutors have yet to show any evidence that Kim’s alleged discussion about the North Korean nuclear program damaged national security. Defense attorneys also say in their cover letter to congressional leaders that they doubt that anyone in the administration has conducted an analysis of whether the prosecution of the alleged leak could cause more potential harm than was actually caused by the leak itself.

In court filings, government lawyers argued — and a federal judge agreed — that the new policy is merely a guide that still gives prosecutors some discretion. Prosecutors also rejected as “misplaced” the analysis by Kim’s lawyers that the new policy requires “proof of harm.”

Machen’s spokesman Bill Miller said Tuesday that the office has been litigating the case against Kim for three years and remains “committed to holding Mr. Kim accountable for his conduct.”

Holder’s revised policy was released in July after a series of meetings with academics, First Amendment advocates and news media organizations, including The Post.

Kim’s lawyers say that the guidelines effectively acknowledge that investigators should not have gathered e-mail records for Fox News reporter James Rosen to build their case against Kim. A search warrant for Rosen’s personal e-mails characterized the reporter as a possible criminal “co-conspirator” in the alleged misconduct even though the department has said it had no intention of charging Rosen.

Under the amended guidelines, such a warrant can be obtained only if the reporter is the target of the investigation.

Kim’s lawyers and federal prosecutors have been engaged in lengthy battles over documents in advance of a trial scheduled for April. Defense attorneys have used similar arguments to try to persuade U.S. District Judge Colleen Kollar-Kotelly that the government’s legal position is inconsistent with the new guidelines and that such cases “require proof of harm that may itself result in further harmful disclosures.”

Kollar-Kotelly has rejected that argument, finding that the government is not required to show harm to make its case. In addition, the judge ruled in an October opinion that the guidelines are advisory and “not intended to create or recognize any legally enforceable right.”