The brief noted that Saudi Arabia is “an international ally of the United States.” The two nations are also allies in the case, which arose from the 2000 bombing of the destroyer Cole in Yemen by Qaeda operatives, an attack that killed 17 American sailors and injured 42 more.

Fifteen of the injured sailors and three of their spouses sued Sudan, saying it had harbored and supported Osama bin Laden and other members of Al Qaeda in the years before the bombing. They won a $314 million default judgment.

Like Saudi Arabia, which faces lawsuits over its role in the Sept. 11 attacks, the Trump administration has taken Sudan’s side in the case, to the consternation of the Veterans of Foreign Wars of the United States. “It is shocking and deeply dismaying that our government would stand with the nation that facilitated the Cole bombing, and against the surviving American sailors and their families,” the group said in a brief.

The legal question in the case, Republic of Sudan v. Harrison, No. 16-1094, is whether the plaintiffs had properly served Sudan by sending the complaint in the case to its embassy in the United States. You might think that is a pretty sensible way to let a foreign nation know about a lawsuit, but a federal statute complicates matters.

It allows service “by any form of mail requiring a signed receipt” sent to “the head of the ministry of foreign affairs of the foreign state.” The law does not specify where the papers must be sent.