Attorney General Yehuda Weinstein's decision to charge Haaretz reporter Uri Blau with "serious espionage" for being in possession of classified Israel Defense Forces documents poses a palpable threat to the free press in Israel, particularly to the ability to criticize government actions and expose them to the public.

As we wrote here a year ago, "trying a journalist for fulfilling his professional mission would constitute a stain on Israeli democracy and do critical harm to freedom of expression."

Issues of war and peace, foreign relations and military operations are at the heart of Israeli public life and take a central place in the country's political and media discourse. For that discourse to take place, there must be reliable media reports from the inner sanctums of senior diplomatic and military officials.

Such media reporting must of necessity rely on "possessing secret reports," in the words of the Penal Code. There's no way to cover the Prime Minister's Office, the defense and foreign ministries, the IDF and the intelligence community without obtaining documents and information that is classified at some level. The Israeli media already operates under military censorship, which doesn't exist in other democracies.

Blau fulfilled his mission and played by the rules: He got information from a source and published parts of that information with the censor's permission. The documents he possessed were for use in his work, and no one claims that he used them for anything else, or that he intended to undermine national security.

At the heart of the indictment being drawn up is a claim by the Shin Bet security service that Blau did not abide by an agreement to return the documents. That's what emerges from the announcement by Weinstein, who is basing his decision to indict Blau on his "conduct."

Weinstein's message is dangerous for democracy. It declares that journalists whose "conduct" doesn't sit well with the authorities risk being tried or even imprisoned. The result is that the media will be deterred from fulfilling its duty and will refrain from reporting on the defense establishment. This outcome is totally unacceptable.

By striving to expose what is happening in the IDF, Uri Blau was working on behalf of all Israelis - and putting him on trial is a dangerous precedent that does serious harm to the public interest.