A dark horse U.S. Supreme Court ruling focused on national security may end up as the most significant decision for business in the court's 2008-2009 term.

Ashcroft v. Iqbal, released in May, will make it harder to bring a lawsuit without specific factual evidence, raising the threshold for moving a case into expensive litigation and possibly saving companies millions of dollars in legal fees. The case was overshadowed by other business rulings on consumer lawsuits, environmental and employment law and other matters in a term set to end on June 29, but legal experts said it may be the most important.

"It's the case that will be cited more than any other by a factor of 100," said Tom Goldstein, partner at Akin Gump, calling the ruling "an unexpected gift for the business community."

In the case, a Pakistani named Javaid Iqbal sued government officials over his detainment after Sept. 11, 2001. The Supreme Court ruled that Iqbal did not have sufficient factual evidence to proceed with his discrimination claims.

"While legal conclusions can provide the framework of a complaint, they must be supported by factual allegations," Justice Anthony Kennedy wrote in the 5-4 opinion. He cited the 2007 decision in Bell Atlantic Corp. v. Twombly, an antitrust case that outlined what plaintiffs must assert to make it through initial court proceedings.

As a result of the Iqbal ruling, businesses may find it easier to fend off lawsuits by convincing courts to dismiss complaints early in litigation.

"Lawyers were citing it within days and putting it in their motions to dismiss," said Jane Willis, partner with Ropes & Gray. "Everyone saw it's a new touchstone."

The decision translates most easily to business cases that list not only a single company, but also its parent company and affiliates, Willis said. The court did not allow Iqbal to assert that government officials had "supervisory liability" for the orders that resulted in his arrest.

More broadly, the opinion clarifies that the Twombly ruling applies beyond antitrust cases. It also makes it harder to press a lawsuit without making more substantive, factual allegations.

Businesses will face the same hurdles if they choose to file a lawsuit, said Robin Conrad, executive vice president of the U.S. Chamber of Commerce's litigation center. "It puts the burden on the person filing the complaint and that applies to businesses too," she said.

Notable in the Iqbal case was a dissent by Justice David Souter, who wrote for the 7-2 majority in the Twombly opinion. Souter said the Twombly decision did not require the court to decide early on if the facts are true, as was decided in Iqbal.

"We made it clear, on the contrary, that a court must take the allegations as true, no matter how skeptical the court may be," he said in the dissent.

Other notable business developments from the term include:

- The Supreme Court - in cases involving Altria Group Inc.'s (MO) Philip Morris unit and Wyeth (WYE) - made it easier for consumers to sue companies over pharmaceutical drug labeling and tobacco advertising in a pair of split opinions that said federal laws don't prevent those lawsuits in state courts. Businesses have used a legal argument known as preemption - that federal statute trumps a state-level proceeding - to beat back consumer lawsuits. The court on Monday will release the outcome of a third preemption case involving New York authorities trying to investigate mortgage lending at national banks.

-Businesses scored a series of wins in environmental law cases, including holdings that made it easier for power plants to avoid expensive upgrades, limited Superfund liability for manufacturers that made toxic products but didn't pollute, upheld a mining waste permit for a unit of Coeur d'Alene Mines Corp. (CDE) and rejected third party challenges to proposed salvage timber leases on national forest lands.

-On the employment law front, the court last week gave businesses a stronger hand in deflecting claims from older workers who allege they were discriminated against because of their age.

-Other opinions of note upheld Federal Communications Commission rules that punish broadcasters for airing obscene language and rejected claims by Internet service providers that sued a unit of AT&T Inc. (T) over the wholesale prices it was charging for access to the company's phone networks.

-By Kristina Peterson, Dow Jones Newswires; 202-862-6619; kristina.peterson@dowjones.com.

(Mark H. Anderson contributed to this report.)