Legislation drafted by Sen. Benjamin L. Cardin to update the 1917 Espionage Act has angered public disclosure advocates who say the proposal would make it harder for federal employees to expose government fraud and abuse.

The bill would clarify a murky area of law to ensure that anyone who publicly leaks classified material could be prosecuted criminally, which is not necessarily the case today. The proposal also would make it illegal for government employees to violate nondisclosure agreements.

Watchdog groups say the measure would make it harder to uncover secret military programs — such as domestic surveillance — because it doesn't provide protection for whistleblowers and ignores a broadly held view that the Pentagon and other agencies are overzealously classifying material.

"The truth is that not everything that is classified is deserving of protection," said Steven Aftergood, who tracks intelligence issues for the Federation of American Scientists. "Moldy old secrets from decades past are still classified."

Cardin counters that the proposal is intended to "deal with the current threats to national security." While he notes his support of separate legislation to bolster whistleblower protections, he says individual employees should not decide on their own when it is appropriate to disclose sensitive material.

"If a document is classified, there is something wrong with people just believing they can release that information to the public," Cardin, a Maryland Democrat, said in an interview.

Cardin introduced the bill in February after holding a hearing on the issue in May 2010, before the WikiLeaks website released thousands of documents dealing with the war in Afghanistan as well as diplomatic cables sent from U.S. embassies. While Cardin said the bill is not motivated by WikiLeaks, he said it is important to national security that the Espionage Act cover leaks.

Passed by Congress at a time when the U.S. was entering World War I, the Espionage Act still makes reference to signal books, photographic negatives and telegraphs as it sets out what types of material relating to "national defense" must not be disclosed.

Broadly, the statute is intended to cover cloak-and-dagger-style espionage.

But the law is increasingly being used to indict those who leak confidential information to the public.

Bradley Manning, the former Army intelligence analyst accused of sending State Department documents and other material to WikiLeaks, was charged in part under the law. Former National Security Agency official Thomas Drake was indicted in 2010 under the act for retaining classified information about a troubled surveillance program for the purposes of leaking it to The Baltimore Sun.

Drake, who won a national award this year for truth-telling, ultimately pleaded guilty to a misdemeanor after federal prosecutors dropped felony charges.

The Espionage Act does not specifically prohibit the release of all classified documents, only material relating to national defense that one could reasonably argue might be used to harm the country. That means classified documents that are diplomatic in nature, for instance, are not expressly covered under the act.

Cardin's bill, which has stalled in the Senate Judiciary Committee, would apply the law to all classified material.

Experts and some advocates acknowledge that federal courts have already interpreted the act to include those documents. But they say that specifically adding them to the Espionage Act would make it easier for the government to prosecute leakers.

The bill "codifies what has already been lurking in the case law but which was not completely settled," said Stephen Vladeck, an American University law professor and an expert on federal courts and terrorism.

Further, the proposal would put the burden on defendants to prove why a document should be public rather than forcing the government to justify why it is classified.

Members of both political parties, including Cardin, say that over-classification is a problem in Washington. The 9/11 Commission named it as contributing to the government's inability to prevent the 2001 attacks, suggesting that excess classification made it more difficult for government agencies to share vital intelligence.

Disclosure advocates say the systemic problem also limits the public's ability to hold government accountable.

"We should be going in the other direction," said Michael Macleod-Ball, chief of staff for the Washington legislative office of the American Civil Liberties Union. "What you need to do is fix the classification system."