(Adds lawyer's comments, details from decision, background, byline)

By Jonathan Stempel

Aug 30 (Reuters) - A federal appeals court on Friday handed a victory to travelers who object to invasive screenings at U.S. airport security checkpoints, saying screeners are not absolutely immune from lawsuits accusing them of abusive conduct.

In a 9-4 decision, the 3rd U.S. Circuit Court of Appeals in Philadelphia said Transportation Security Administration screeners were "investigative or law enforcement officers" for purposes of searching passengers, waiving the government's usual immunity from lawsuits.

Circuit Judge Thomas Ambro said the "intimate physical nature" of airport screenings brought them within the ambit of law enforcement, allowing travelers to pursue some civil claims under the Federal Tort Claims Act for intentional wrongdoing.

He downplayed concern that the decision would open the floodgates to litigation, saying that in 2015 fewer than 200 people, out of more than 700 million screened, filed complaints that might trigger the waiver.

"The overwhelming majority of perform their jobs professionally despite far more grumbling than appreciation," he wrote. "Their professionalism is commensurate with the seriousness of their role in keeping our skies safe."

Friday's decision reversed a July 2018 ruling by a three-judge 3rd Circuit panel.

It is a victory for Nadine Pellegrino, a business consultant from Boca Raton, Florida, who with her husband sued for false arrest, false imprisonment and malicious prosecution over a July 2006 incident at Philadelphia International Airport.

Pellegrino, then 57, had objected to the invasiveness of a random screening prior to her scheduled boarding of a US Airways flight to Fort Lauderdale, Florida, and was accused of striking a TSA officer.

She was eventually jailed for about 18 hours and charged with assault, making terroristic threats and other crimes, which she denied. Pellegrino was acquitted at a March 2008 trial.

"If you think you are a victim of intentional misconduct by TSA agents, you can now have your day in court," her lawyer Paul Thompson said in an interview. "Nadine never gave up, and it is a real tribute to her courage."

The Department of Justice, representing the TSA, did not immediately respond to requests for comment.

Circuit Judge Cheryl Ann Krause dissented from Friday's decision, saying it exposed the government to "vast" potential liability that Congress did not clearly intend.

She also said the majority split from other federal circuit courts by failing to distinguish TSA screeners from FBI agents, immigration agents, postal inspectors, customs officers and others with traditional police powers.

"I am sympathetic to the concern that the current legal regime provides no obvious remedy" to people like Pellegrino, but expanding the immunity waiver "lies beyond our purview," she wrote.

The case is Pellegrino et al v U.S. Transportation Security Administration et al, 3rd U.S. Circuit Court of Appeals, No. 15-3047. (Reporting by Jonathan Stempel in New York Editing by Matthew Lewis)

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