Elected on a promise of a more transparent government, President Barack Obama has taken "unprecedented" aim at leakers who divulge classified information to journalists, critics say.
"We've seen the current president bringing five prosecutions so far... against people for whistleblowing, for leaks of classified information," said Daniel Ellsberg, famous for his 1971 leak of the "Pentagon Papers," which helped turn the tide of public opinion against the Vietnam War.
"All previous presidents put together brought three prosecutions... We see a campaign here against whistleblowing that is highly unprecedented in legal terms."
The White House declined to answer questions about its policy towards those who leak government secrets.
Manning, 23, was arrested in June while deployed to Iraq, amid suspicions he was responsible for passing a trove of secret US government documents to the whistle-blowing website, many of which were then published around the world.
Earlier this month, the military unveiled 22 additional charges against Manning including "aiding the enemy", which carries a potential death sentence, though the army said it would not seek capital punishment.
US investigators have failed so far to establish a direct link between the Manning and the website, which began publishing the documents last year.
Rights groups have criticized the conditions of Manning's detention at a Marine base in Quantico, Virginia.
Despite the barrage of prosecutions, experts say the government will have a heavy burden in proving its case under a 1917 espionage law.
"One of the statutes says that you have to give this information... 'with the intent or reason to believe that this information is to be used to the injury of the US'," said Andrew Contiguglia, an expert on constitutional law.
"In the situation that you have here, there are former CIA operatives, military operatives, taking the information and giving it off to press people, not spies," he said.
"What makes us think that when we give information to the press, that info is going to be used to the injury of the US?"
He goes on to argue that the leaks are part of the American system.
"It's important that in order to strenghten our democracy, we have to keep our government honest, and the only way to keep our government honest is to give access to that information," he said.
"All presidents and all national security branch officials worry about unauthorized leaks," he said.
"There's always been a great concern in the governments about leaks of damaging national security information, and I don't think that's changed dramatically from one administration to another."
He added that there is a bit of a double standard at play.
"There is a certain amount of hypocrisy," Marcus said.
"There are good reasons for the government trying to keep certain information secret (but) government officials often leak some information when they believe it is in the interest of the government to do so."
Source: AFP American Edition