WASHINGTON — The Supreme Court on Wednesday struggled with whether to put a new roadblock in the way of terrorism victims trying to obtain nearly $2 billion in judgments against Iran.

The justices heard arguments between Bank Markazi, Iran’s central bank, and relatives of terrorism victims, including many who were among the 241 Marines killed in Lebanon in 1983.

The issue is whether Congress butted into the business of federal courts when it passed a 2012 law allowing the families to be paid from assets of the central bank that are held in the United States.

Several justices raised questions about whether Congress impermissibly tried to dictate the outcome of the dispute. Chief Justice John Roberts said it is “our job to decide cases.”

On the other side, Justice Stephen Breyer suggested that Congress and the president, who signed the law, have broad authority when it comes to foreign affairs.

Congress has repeatedly changed the law in the past 20 years to make it easier for victims to sue over state-sponsored terrorism and federal courts have ruled for the victims. But actually collecting the money has proved difficult.

A decision in Bank Markazi v. Peterson, 14-770, is expected by late June.