When the agreement went into effect, there were 21 newspaper joint operating agreements around the country, Justice Department spokeswoman Gina Talamona said.
She said six remain, in Detroit, Charleston, W.Va., Fort Wayne, Ind., York, Pa., Salt Lake City and Las Vegas.
Justice Department officials were reviewing proposed changes to the Las Vegas joint operating agreement, Talamona said.
Eric Witkowski, the Nevada state attorney general's consumer advocate, observed the proceedings and declined comment.
Greenspun attorney Joseph Alioto of San Francisco urged Mahan to stop the Stephens Media effort. The Newspaper Preservation Act clearly prohibits one partner in a joint operating agreement from buying the other, he said.
Instead, Mahan, who began the hearing lamenting the slow death of the Las Vegas Sun, ended saying that he had no dispute to decide.
"There's no contract here. There's no agreement," the judge said. "I think the suit is premature."
Mahan noted that he gave both sides advance notice of his opinions in a four-page order Aug. 27 that characterized Brian Greenspun as a dissident minority board member in the Greenspun Corp. and Las Vegas Sun Inc.
The judge outlined his reluctance to have the court oversee Las Vegas newspaper operations and noted the deaths of newspapers in cities including Seattle, Honolulu and Nashville, Tenn.
Mahan also mentioned the passage of Newsweek and U.S. News and World Report magazines, and said he thought the public preferred to get news from the Internet and television.
"I prefer a two-newspaper town. Not because of the two political parties ... but because the two newspapers emphasize different things," the judge said. "But the times are changing."
Stephens Media attorneys have called the printed Sun a financial drain that costs more than $1 million a year to produce and distribute.
Greenspun pointed in court documents to the effects of the Great Recession and said that since 2008 annual joint operation payments from Stephens Media to the Sun have dropped almost 90 percent, from about $12 million to about $1.3 million a year.
A 2005 amendment to the Las Vegas agreement ceased afternoon publication of the Sun. The combined newspapers circulate some 252,000 copies on an average weekday. The Sun no longer has a printing press.