by KYW's Michelle Durham

Attorneys from a Philadelphia law firm were in front of a federal judge on Friday on behalf of the families of victims of the September 11th terrorist attacks.

The plaintiffs want to be able to sue the government of Saudi Arabia and key members of that country's royal family.

In 2005, a judge said no -- the Saudi government and royal family were protected against US federal legal action.

And according to Temple University law professor Jeffrey Dunoff, in order for the case to proceed, Saudi Arabia would have to be on the US government's list of "sponsors of terrorism" -- which it isn't:

"The threshold question is when a foreign state can be sued for terrorism in a US court. And the answer is, only when that state appears on a US government list as a state sponsor of terrorism. And Saudi Arabia is not currently on that list. And so as a matter of law it's virtually impossible for this suit to go ahead against the government of Saudi Arabia."

And Dunoff said the US government's position may be reasonable:

"The government has lots of interests in not seeing this suit go ahead. The executive branch may say to the court, 'Look, we're working with Saudi Arabia right now to keep down the cost of oil, to move ahead on a peace plan with the Palestinians and the Israelis to try to fight terrorism.' " 

An adverse judgement from a court could threaten all of that. And Dunoff says those issues will certainly be on the mind of the judge as he makes his decision.

But Dunoff does feel the suit against several Saudi charities will be able to proceed.

In 2003 the Philadelphia law firm of Cozen O'Connor was the first in the nation to file a lawsuit against Saudi Arabia and the royal family on behalf of 9/11 victims.