Senators voted by a surprisingly high 44-24 margin for the law, celebrating the end of dictatorship-era rules that enabled a few companies to dominate Argentine media. Opponents say it instead gives the government too much power and will curtail freedom of speech.
The new law preserves two-thirds of the radio and TV spectrum for noncommercial stations, and requires channels to use more Argentine content. It also forces Grupo Clarin, the country's leading media company, to sell off many of its properties.
"The initiative is moderate and democratic," said Sen. Miguel Angel Pichetto, a ruling party leader, during nearly 20 hours of uninterrupted debate that ended Saturday morning. "It allows for companies to have an adequate position, but not a dominant one."
Opponents say the new law simply replaces a media oligopoly with a state monopoly _ and will enable investors with close ties to the president and her husband, former president Nestor Kirchner, to snap up media properties at low prices in forced sales.
Outside Congress, thousands of supporters celebrated in the plaza with chants, applause, fireworks and booming drums. The demonstration was organized by government supporters and included political activist Maximo Kirchner, son of the first couple.
Ruling party Sen. Liliana Fellner said the law does away with a vestige of Argentina's 1976-83 military dictatorship.
"We are settling an old debt with democracy," she said.
The commission applying new regulations and granting (or canceling) radio and television licenses will have seven members, include two designated by the executive branch, three by Congress and two by a federal body representing provincial governments. This should ensure ruling party control, which opponents fear will be used to threaten and censure critics.
Most affected is Grupo Clarin, one of Latin America's leading media companies. Within one year, it must sell off radio stations, television channels and part of its dominant cable TV network to comply with new ownership limits.
"The government is going after the media with all its remaining power," Clarin Editor Ricardo Roa wrote Saturday. "It has rushed through a misleading law that seems to be progressive but in reality only sets us back: it will promote a press that is weaker and more docile."
The lopsided Senate vote makes it unlikely the law will be overturned when Fernandez loses supporters in a new Congress, starting Dec. 10. A two-thirds majority in needed to overcome her veto.
The new law imposes more frequent licensing approvals, and requires that at least 70 percent of radio content and 60 percent of television content be produced in Argentina. It also requires cable TV companies to carry channels operated by universities, unions, indigenous groups and other non-governmental organizations.
Clarin and other media companies will now go to the courts, saying the new limits violate constitutional property protections. Cabinet Chief Anibel Fernandez said Saturday that "this is the right of any citizen."
Associated Press Writer Vicente Panetta contributed to this report.