WASHINGTON (Reuters) - U.S. Supreme Court justices expressed skepticism on Monday over whether ancient Persian artifacts held in a Chicago museum can be seized to pay for a $71 million court judgment against Iran won by several Americans injured in a 1997 Jerusalem bombing who accused Tehran of complicity in the attack.

The court heard arguments in the plaintiffs’ appeal of a 2016 ruling by a federal appeals court blocking the artifacts, including clay tablets boasting some of the oldest writing in the world, from being turned over to them to help satisfy the court judgment that Iran declined to pay.

The dispute concerns the Foreign Sovereign Immunities Act, a federal law that largely shields foreign governments from liability, and their assets from seizure, in American courts, except for countries designated by the U.S. government as state sponsors of terrorism, a list that includes Iran.

Iran is one of several countries and organizations ordered by U.S. courts to pay damages in similar cases, though such orders have been difficult to enforce.

After Iran refused to pay the judgment, the plaintiffs targeted ancient Persian artifacts including objects held at the University of Chicago’s Oriental Institute on loan from Iran since 1937.

The law exempts from immunity certain foreign-owned property used for commercial purposes in the United States. The lower court ruled that the exemptions cover only property used by the foreign state and not by a third party like the university.

Some of the justices questioned whether non-commercial property like the artifacts may be seized. Justice Sonia Sotomayor told the plaintiff’s lawyer, Asher Perlin, that it seemed like an issue the U.S. Congress should address.

“I don’t think there will be a mad rush to grab antiquities,” Perlin replied.

When Justice Stephen Breyer pointed out that Perlin’s clients were doing just that, Perlin suggested they had no choice because Iran does not pay judgments no matter what American courts say.

“The idea that Congress would be concerned with affronting the dignity of a state sponsor of terrorism and would extend protection to their non-commercial assets for that reason ... is just preposterous,” Perlin added.

The long-running Chicago lawsuit arose from a 1997 attack in which three members of the Islamic militant group Hamas blew themselves up at a crowded pedestrian mall in Jerusalem, killing five people. Eight injured U.S. citizens, including lead plaintiff Jenny Rubin, and their relatives sued Iran in a U.S. court alleging it had provided support for the group. The court agreed, awarding them $71.5 million, which they then sought to collect.

President Donald Trump’s administration sided with Iran and the university, warning that litigation against foreign states in the United States can affect the reciprocal treatment of the United States in foreign courts.

Eight of the nine justices took part in the argument, with Justice Elena Kagan recusing herself. A decision in the case is due by the end of June.