Hidden in the back streets of Mumbai is the Chabad House. In late November 2008, this quiet synagogue and hostel run by American Rabbi Gavriel Holtzberg and his pregnant wife Rivka became the scene of their brutal murders, part of Pakistani terrorist group Lashkar-i-Taiba’s relentless three-day siege on the city that left 166 dead, including six Americans.

More than four years later, the Holtzberg family and the American relatives of five others killed in the attacks are still looking for justice, but are hitting critical roadblocks.

Earlier this week the State Department announced that two former Pakistani intelligence directors, Ahmed Shuja Pasha and Nadeem Taj, are immune from the wrongful death lawsuit the families filed against Lashkar and Pakistan’s main intelligence agency, the Inter-Services Intelligence (ISI), in a federal court in New York.

“In the view of the United States, the Inter-Services Intelligence is entitled to immunity because it is part of a foreign state within the meaning of the Foreign Sovereign Immunities Act,” U.S. Principal Deputy Assistant Attorney General Stuart Delery wrote in an affidavit on Monday. The State Department also noted that the determination was “not subject to judicial review.”

A joint investigation by FRONTLINE and ProPublica last year revealed that David Coleman Headley, the Pakistani American who has admitted scouting targets for the attacks, was also a spy for Pakistani intelligence. In trial testimony last year, Headley, who is scheduled to be sentenced in January, gave an unprecedented account of how Lashkar carried out the attacks with the support of ISI officials.

That testimony serves as critical evidence in the lawsuit, says the families’ lawyer James Kreindler, who was also part of the successful suit against Libya for the 1988 bombing of Pan Am Flight 103 over Lockerbie, Scotland. Kreindler says his claimants are asking for the same amount — $10 million — in compensation for each death claimants in the Lockerbie suit received. “They just want to be treated fairly, consistently,” he told FRONTLINE. Despite the State Department setback, he says they are determined to press ahead.  “We’re moving forward no matter what.”

Bonus: Building and Re-Building the Chabad House:

A chronicle of what happened at the Jewish community center targeted by the Mumbai terrorists, and how family members of those killed are moving forward.