The court ruled that a new law, which stipulated that upbeat news should make up half of all newscasts on Romania's radio and television stations, was unconstitutional.
The senate had passed it unanimously the previous month.
The opposition liberal democrats, the PDL party, had appealed to the constitutional court, arguing that the new legislation infringed freedom of expression.
The law had been the idea of two senators -- one from the governing National Liberal Party, the other from the far-right Great Romania party -- who bemoaned the "irreversible effect" of negative news "on the health and life of people.
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The aim, they said, was to "improve the general climate and to offer to the public the chance to have balanced perceptions on daily life, mentally and emotionally".
It would be left to the National Audiovisual Council in Romania to judge what is "positive" and "negative".
But the coucil itself was unimpressed by the new law.
until the 1989 collapse of communism.