Allan Gerson, a Washington lawyer and legal scholar who helped pioneer the practice of suing foreign governments in U.S. courts for complicity in terrorism, representing victims’ families in the aftermath of the Lockerbie bombing and the 9/11 terrorist attacks, died Dec. 1 at his home in the District. He was 74.

The cause was complications of Creutzfeldt-Jakob disease, a degenerative brain disorder, said his wife, cookbook author Joan Nathan.

Mr. Gerson was an author, ­private-practice lawyer, former professor at George Mason University and deputy assistant attorney general under President Ronald Reagan, known for representing victims of human rights abuses and terrorist attacks. He also distinguished himself as a photographer, with work collected at the International Photography Hall of Fame Museum in St. Louis, and as a jewelry designer who turned some of his images into brooches.

The son of Jewish refugees from Poland, he came to the United States under a false name in 1950 and later identified as a former “dreamer,” likening himself to the roughly 700,000 undocumented immigrants who arrived in the country as children and may soon be subject to deportation under the Trump administration. “But for dint of circumstance,” he wrote in a 2017 essay in The Washington Post, “I might be in their boots.”

As a young Justice Department trial lawyer, he pursued Nazi war criminals who had immigrated to the United States, later rising to become senior counsel to two U.S. ambassadors to the United Nations, Jeane J. Kirkpatrick and Gen. Vernon A. Walters.

Throughout, he maintained that the law had a decisive role in public policy and international affairs — a belief that drove his decade-long fight for justice for the victims of Pan Am Flight 103, which exploded over Lockerbie, Scotland, on Dec. 21, 1988, en route to New York from London.

Notable deaths in 2019: Elijah Cummings, Cokie Roberts, Toni Morrison and others we have lost this year

Don Imus | Don Imus, who spent more than half a century in radio and television skating along the edge of propriety and occasionally falling into the abyss of the unacceptable, died Dec. 27 at a hospital in College Station, Tex. He was 79. In a roller-coaster career in which he grew chummy with prominent politicians, repeatedly got suspended or fired for offensive cracks, abused drugs and touted health foods, Mr. Imus won a loyal following, made millions and transformed himself from a bad-boy DJ into a host whose program became a nearly mandatory stop for presidential candidates. Read the obituary (Richard Drew/AP)

The bombing killed all 259 passengers and crew — along with 11 people on the ground — and remains the deadliest terrorist attack in British history. Among the victims were 189 Americans, including many study-abroad students from Syracuse University.

Mr. Gerson launched what began as a seemingly quixotic legal effort, seeking to obtain compensation for victims’ families from the government of Libyan ruler Moammar Gaddafi, which was accused of carrying out the bombing. His work spurred new legislation that paved the way for lawsuits against countries including Syria, Cuba, Iran, Saudi Arabia and Libya, where a legal team negotiated a $2.7 billion settlement in 2003 for the Lockerbie bombing.

“It took a lot of creative lawyering to come up with a system that would enable those victims to recover,” said Beth Van Schaack, an international criminal lawyer who teaches human rights at Stanford Law School. “There was no long history of precedents to draw on,” she added. “They were making stuff up as they went along . . . and now it’s become a standard practice. If a terrorist attack happens, there are lawyers who specialize in this area.”

Mr. Gerson’s work on the case emerged out of a 1992 op-ed he wrote in the New York Times, calling for the United Nations to create a claims commission to compensate survivors’ families using Libyan assets. His article caught the attention of Bruce M. Smith, a former Pan Am pilot whose wife was killed in Lockerbie and who retained Mr. Gerson in an effort to bring the U.N. proposal to fruition.

That idea never took off, leading Mr. Gerson to launch his campaign to sue Libya for damages — a gambit that tested the centuries-old doctrine of sovereign immunity, in which governments are effectively considered above the law, not subject to civil suits or criminal prosecution without their consent. It was also unusual in that Mr. Gerson was representing just one of the victims’ relatives, Smith, with other families taking part in a suit charging Pan Am with negligence for failing to detect the bomb.

“If we’d known all the difficulties at the outset,” he later told Washington City Paper, “we probably never would have proceeded.”

Mr. Gerson partnered with a recent law school graduate, Mark S. Zaid, and filed suit in a federal court in New York in 1993. By then, he had been forced out of the Washington office of Hughes Hubbard & Reed, where a colleague was hired to take on Gaddafi as a client, resulting in a conflict of interest.

Their case proved unsuccessful amid sovereign immunity concerns. But as it proceeded, Mr. Gerson and Zaid embarked on a new tack, drafting and championing what became the 1996 Anti­terrorism and Effective Death Penalty Act, which enabled lawsuits against countries designated by the State Department as state sponsors of terrorism.

In a phone interview, Zaid said he took the lead on drafting the legislation but credited Mr. Gerson with overseeing the broader strategy, and with helping to forge political connections that smoothed its passage in Congress.

“He was very much a visionary, trying to come up with innovative legal theories to pursue claims that other people would have written off without any second thought,” he said. “He saw in his mind a path forward to accomplish justice, especially for these victims of terrorism that no one else was thinking of at the time.”

The legislation was signed into law following another terrorist attack, the 1995 bombing of a federal building in Oklahoma City. After Libyan intelligence officer Abdel Basset Ali al-Megrahi was convicted of the Lockerbie bombing in 2001, a civil suit against Libya moved ahead, resulting in $10 million compensation for each victim, paid out over several years from an escrow account in a Swiss bank.

In 2016, Congress overrode President Barack Obama’s veto of the Justice Against Sponsors of Terrorism Act, which carved out further exemptions to sovereign immunity and enabled 9/11 victims’ families to sue Saudi Arabia for its alleged support for the Sept. 11, 2001, terrorist attacks.

Mr. Gerson was part of a team representing many of the families, and the case was still working its way through the courts when he died.

“There is a famous quote, that the wheels of justice grind infinitely slow but infinitely fine,” he told City Paper in 2002, while still awaiting resolution on Lockerbie. “Unfortunately, all I’ve seen is that the wheels of justice grind infinitely slow.”

Allan Gerson was born in Samarkand, then part of Soviet Uzbekistan, on June 19, 1945. His parents had spent part of World War II in Siberian labor camps and moved south to get closer to the British mandate of Palestine — and for warmth, his family said.

His father had previously worked as a bookkeeper at his family’s candy store in Zamosc, Poland, and his mother was a dressmaker. They moved to a displaced-persons camp in Germany, where they adopted a false identity, Blumstein, to receive immigration visas belonging to another family that had decided to move elsewhere.

“Had they not done so,” Mr. Gerson wrote in The Post essay, “they would have been turned away from the United States — they had no sponsors, and the entry quota was severe.” They settled in New York City, where his father eventually opened a dry-cleaning shop in the Bronx and the family obtained U.S. citizenship under their original names.

Mr. Gerson studied economics at the University at Buffalo in New York, graduating in 1966. He received a law degree from New York University in 1969, a master of laws degree from the Hebrew University of Jerusalem in 1972 and a doctor of juridical science from Yale University in 1976.

He joined the Justice Department as a trial lawyer the next year and eventually moved to the Office of Special Investigations, where he pursued former Nazi criminals. Many were deported through civil proceedings.

Mr. Gerson was named Kirkpatrick’s senior counsel in 1981 and later chronicled those years in a book, “The Kirkpatrick Mission: Diplomacy Without Apology” (1991). He was later a senior fellow at the American Enterprise Institute and the Council on Foreign Relations, and wrote books including “Israel, the West Bank and International Law” (1978) and “Privatizing Peace: From Conflict to Security” (2002) with Nat J. Colletta.

His clients in recent years included Pierre Konowaloff, who said that Vincent Van Gogh’s painting “The Night Cafe,” now owned by Yale, was seized from his family during the Russian Revolution. A federal appeals court ruled against him, and in 2016 the U.S. Supreme Court declined to hear the case.

In addition to his wife of 45 years, of Washington, survivors include three children, Daniela Gerson and David Henry Gerson, both of Los Angeles, and Merissa Nathan Gerson of New Orleans; a brother; and two grandchildren.

Mr. Gerson developed close relationships with some of the families of the Lockerbie bombing victims and discussed their plight in “The Price of Terror” (2001), written with journalist Jerry Adler. The book also covered the legal drama surrounding the terrorist attack, looking somewhat optimistically toward the future.

“Terrorists who might be undeterred by the threat of American military force,” the authors wrote, “must now weigh the possibility of retaliation by the world’s largest contingent of lawyers.”