Lawyers for NBC Universal Inc., had asked the high court to overturn a lower court order that the cable TV news network include the Ohio congressman or pull the plug on broadcasting the debate Tuesday night with Hillary Rodham Clinton, Barack Obama and John Edwards.

An hour before the debate, the state Supreme Court's unanimous order said that blocking the debate unless Kucinich got to participate would be "an unconstitutional prior restraint" on the news network's First Amendment rights. The justices also said the lower court exceeded its jurisdiction by ordering Kucinich's participation even though he first requested and was denied relief from the Federal Communications Commission.

"It's a matter of being on stage and answering questions. That's the issue," lawyer Bill McGaha argued for Kucinich during a hearing before four justices in Las Vegas. Three other justices participated by closed-circuit video conference from Carson City.

Donald Campbell, a Las Vegas lawyer representing NBC Universal, accused Kucinich of trying to make a jurisdictional "end run" around the FCC and federal courts by suing in Nevada state court to be added to the debate.

FCC broadcast rules do not apply to cable TV networks, Campbell said, adding that forcing MSNBC to add Kucinich or not broadcast the debate amounted to prior restraint and would be a "clear and unequivocal" violation of First Amendment press freedom.

"Mr. Kucinich's claim ... undermines the wide journalistic freedoms enjoyed by news organizations under the First Amendment," Campbell said in his appeal.

Campbell said MSNBC decided to go with the top three candidates after the Iowa and New Hampshire primaries. Kucinich drew less than 2 percent of the Democratic vote in the New Hampshire primary, after attracting little support in the Iowa caucuses.