Striking National Football League players may be back in action a week from Sunday on the playing field, but their lawyers are preparing for a high-stakes battle with league owners that could determine the power balance between players and management for years to come.

That fight will be waged in a federal courthouse in Minneapolis, where the players union filed a lawsuit Thursday against the owners, accusing management of violating federal antitrust laws.

Lawyers on both sides agree that a collective bargaining agreement protects owners from antitrust lawsuits even if they take actions -- such as setting up the player draft or restricting free agency -- that might otherwise be found to improperly restrain players' economic freedoms.

The key issue, according to lawyers on both sides, is whether that exemption from the antitrust laws applies when there is no collective bargaining agreement. The union says it does not apply; management says it does.

The lawsuit, which some sources called a pre-emptive strike to thwart legal action by management, puts the players on friendly ground. They won a similar antitrust lawsuit in Minneapolis 11 years ago.

A court there, after a 55-day trial, said that, in the absence of a collective bargaining agreement, the owners could be sued for violating antitrust laws prohibiting them from getting together to restrain trade. The Eighth U.S. Circuit Court of Appeals upheld that ruling, and both sides settled the issue in subsequent negotiations.

Union general counsel Dick Berthelsen said the 1976 appeals court ruling means the owners are liable for triple damages after the season ends and players can claim to be free agents. "If it can be shown that the players could have gotten more" but were prevented from doing so by the league, he said, then the owners "will be paying substantial sums. This means they would be restricting free agents at their own risk," he said.

"The owners have said there is never going to be a change in free agency," Berthelsen said. "They are wrong about that legally and if they can't . . . change that, then the court has to tell them so."

Several labor and antitrust lawyers said the lawsuit was a chip to strengthen the union's bargaining position, but Berthelsen insisted that "this is not some ploy to exact concessions at the bargaining table."

The owners are expected to counter with a relatively new antitrust theory.

Under that theory, once there is a union bargaining for all the players, antitrust laws cannot be invoked whether there is an agreement or not. "If the union disbands," explained owners outside counsel Paul Tagliabue, then the owners would become subject again to the antitrust laws. But as long as the union is collectively bargaining for the players, he said, the owners cannot be sued for violating antitrust laws.

If the theory is not convincing to the Eighth Circuit, the owners hope it may convince either the Third U.S. Circuit Court of Appeals in Philadelphia, which could be reviewing a similar lawsuit filed two weeks ago by National Basketball Association players, or to the Supreme Court.

The union, Tagliabue said, "wants to have its cake and eat it, too," saying that collective bargaining rules must control large segments of the negotiations -- but not all.

But Larry Fleisher, executive director of the basketball players' union, said the owners' argument would mean that one collective bargaining agreement would forever free owners from antitrust laws. "Just because you're pregnant once doesn't mean you're always pregnant," Fleisher said.

"They {the owners} are saying that they can have any conditions they want because as long as they have a collective bargaining relationship {with the union} then they can impose unilaterally these restrictions on players such as the draft or non-free agency," Fleisher said.

"Nobody is saying that these things {such as the player draft} are not a violation of the antitrust laws." He said the "only question" for both the NFL and NBA is "whether there is an exemption from the antitrust laws in the absence of a collective bargaining agreement."

Stephen Ross, a professor at the University of Illinois who specializes in antitrust and sports law, predicted the players will win the courtroom battle, but that victory may not get them much.

But the legal victory may not mean much given the "ultra-hard line" management has adopted, he said, and the power management retains. "The players will have an antitrust victory just like they did 11 years ago," he said, but the union likely will lose dues check-offs and other benefits.

A protracted legal battle could take two years or more, Ross said, but he predicted that "by the time the season starts next fall there will be a collective bargaining agreement which will moot out any antitrust suit."