WASHINGTON  Calls to prosecute the founder of WikiLeaks, Julian Assange, mounted this week as his organization began releasing documents from a cache of 250,000 State Department cables  its third major disclosure of United States government secrets this year.

Attorney General Eric H. Holder Jr. has confirmed that the Justice Department is examining whether Mr. Assange could be charged with a crime, but legal scholars say that such an effort would encounter steep legal and policy difficulties.

“There is a haze of uncertainty over all of this,” said Stephen I. Vladeck, an American University law professor who has written about the Espionage Act, a 1917 law that prohibits the unauthorized retention or transmission of defense-related documents.

“The government has never brought an Espionage Act prosecution that would look remotely like this one,” he said. “I suspect that has a lot to do with why nothing has happened yet.”