Argentina's Supreme Court has ruled that a media bill passed in 2009 is constitutional—clearing the way for the break-up of large media groups.
The country's biggest broadcasting and newspaper company, Clarin, had appealed against the law proposed by President Cristina Fernandez de Kirchner.
Critics say the bill is an attempt to silence opposition voices in Argentina.
Supporters say it will boost pluralism and reduce the dominance of big corporate interests.
Following the ruling, Clarin's share price fell nearly 6% and sales had to be suspended.