WASHINGTON - The case against two former pro-Israel lobbyists accused of illegally disclosing classified information has experienced serious setbacks in the past week, jeopardizing the prosecution's ability to win its case.

Most recently, on Tuesday, a federal appeals court ruled that the defendants, former American Israel Public Affairs Committee staffers Steve Rosen and Keith Weissman, can use some classified information at their trial. The court also refused to revisit a lower court decision that sets a high bar for the prosecution to be able to prove wrongdoing.

Those judgments followed a decision Friday by the Federal District Court Judge presiding in the four-year-long case, Thomas Ellis, that William Leonard, a former US official responsible for overseeing the whole classification system, could appear on behalf of the defense. He is expected to testify that classified information has been regularly disclosed to civilians such as lobbyists and journalists to promote administrations' national security policies.

Rosen and Weissman have argued that they committed no crime by passing on the information they'd received, since the practice has long been common in Washington with no legal repercussions. The prosecution has made a rare invocation of the 1917 Espionage Act, applying it for the first time to lobbyists, though the two defendants have not been accused of spying.

"The prosecutors have suffered a string of losses in court which will make it difficult or impossible for them to successfully convict these defendants," assessed Steven Aftergood, director of the Project on Secrecy for the Washington-based Federation of American Scientists.

He said the decision to let the 2006 ruling stand "imposes a very demanding burden of proof on the prosecution" in which the prosecution needs to prove not only the facts of the case but that the defendants knew they were committing a crime, which they deny. "That's a very hard standard to be met."

Additionally, he described Ellis's ruling allowing Leonard's testimony as "a serious blow because the prosecutors don't really have anyone of his stature and experience testifying on their side."

The government could appeal Tuesday's ruling to the full appeals court or the US Supreme Court, which would likely once again delay the trial, now scheduled for April 21. The decisions also raise the question of whether the government will abandon the case, particularly since a new administration has taken over the Justice Department.

"We are reviewing the decision and will respond in court," said Peter Carr, a spokesman for the US attorney's office in Alexandria, where the case is being heard.

Rosen's lawyer, Abbe Lowell, said he could not speculate on how the change in administrations might affect the case, but maintained that the case, begun during the Bush administration, "represents all the things President Obama said should not occur in a government that's more respectful of free speech."

Aftergood suggested that assessment might be "self-serving," though he noted he himself was interested in the case in part because of its implications for free speech and the dissemination of information to journalists and other professionals who also routinely receive classified information from US officials.

"If somebody in the Justice Department is inclined to drop the case, the recent rulings could provide them a pretext," he said, pointing out that the Obama administration, with its different policy approach, might want to abandon the effort.

At the same time, he noted that controversial Bush-era cases involving detainees' rights and other legal issues haven't been dropped by the Obama administration despite widespread expectations that they would be.

He said that justice officials could feel that "the government has invested so much time and money in this case, it's too late to simply say never mind."

AP contributed to this report.