It looks like there’s a new red line in the Middle East. It has been laid down by the judges who ride the second United States appeals circuit, which just let the Palestinian Authority off the hook for killing Americans.

It’s a stunning decision that may be the beginning of the end of a decades-long effort to use civil law to hold accountable those responsible for the murder of Americans abroad. What a bitter pill for surviving families who turned to the courts when our presidents refused to act.

What fodder, too, for our presidential campaign, in which the kind of federal judges we want is one of the issues. The three judges who just ruled for the Palestinians were appointed by William Clinton and Barack Obama.

The case involves an effort by 11 American families who, after losing loved ones in terror attacks in Israel, sued the Palestine Liberation Organization and the Palestinian Authority. They won big last year in federal district court in Manhattan.

This particular case involved several different attacks. The most famous of the group was the 2002 bombing of a cafeteria at the Hebrew University in Jerusalem. That attack killed nine and wounded around 100 others. Five American students were among the dead.

Not only did a jury find that the Palestinians had done the deeds at issue in these cases but they awarded $218.5 million in damages. Under the law, known as the Anti-Terrorism Act, the damages were automatically tripled, to $655.5 million.

The appeals judges threw all that out on the grounds that the district court never should have asserted its jurisdiction over the case in the first place. It instructed the lower court to dismiss the claims.

It’s not my purpose here to get into the fine points of federal law on which the judges ruled in this case. I’ve been warning for years of the disappointments that are going to accrue if we leave the war to civil court.

That began in the 1990s, when a Brandeis coed from New Jersey, Alisa Flatow, was slain in Israel in a bus bombing backed by Iran. Her heroic father, Stephen Flatow, eventually won a legal judgment against Iran of $247 million.

The Clinton administration actually fetched up in court to oppose Flatow’s efforts to collect on the judgment. It feared that the court would upset diplomatic immunity. It bought out the Flatow claim for six cents on the dollar yet now we’re shipping billions to Iran.

This latest case involves attacks by Palestinians against Americans and which the Palestinian Authority praised and rewarded perpetrators financially.

Yet America has launched no military strikes against the Palestinian regime, nor even against Hamas, which claimed credit for murdering the Americans. Instead, it hectors Israel against “disproportionate” responses to terror and tries to get it to be more forthcoming in negotiations.

No wonder the families tried civil law. The Anti-Terrorism Act, under which they sought justice, provides that any American national injured by international terrorism — or his estate or heirs — can sue.

When they won in lower court, though, Obama had his deputy secretary of state file a declaration in court warning against getting too tough. It’s a classic of the administration’s thinking.

Team Obama insisted that it supports “just compensation” for families of those the Palestinian terrorists killed or injured. It’s just that the administration has “significant concerns” about the “harms that could arise.”

It was worried that the Palestinian Authority’s ability to operate as a government might become “severely compromised.” Even, it seems, if Congress didn’t share that worry when it passed the Anti-Terrorism Act.

How much, if at all, the administration’s declaration swayed the appeals court is hard to gauge. In the end, the judges said that “no matter how horrendous” the attacks on the Americans, the lower court had gone beyond the limits allowed by the Constitution.

So 14 years after the Americans were killed or injured, the survivors and their loved ones are out of luck. One of their lawyers, Kent Yalowitz, called it a “cruel decision,” noting that the very terrorists who prompted the anti-terrorism law have now avoided responsibility.

The Palestinian Arabs are gloating. Reuters is quoting their regime’s finance minister, Shukri Bishara, as calling the Second Circuit’s decision “a big blow to anyone who attempts to blackmail us.”

“We have drawn a red line under it,” Mr. Bishara added, just to bring the matter full circle. It’s an ironical turn of phrase, given how Mr. Obama and Hillary Clinton seem to feel about red lines.

This column first appeared in the New York Post.