This file photo taken on September 11, 2001 shows a hijacked commercial plane approaching the World Trade Center. (Seth Mcallister/AFP/Getty Images)

A BASIC precept of international law is that sovereign nations, or their government officials, should not be liable for official actions in the civil courts of other sovereign nations. Sovereign immunity has stood the test of time because it makes practical sense. And it makes practical sense because the international deeds and misdeeds of governments are more equitably dealt with through state-to-state negotiations than by hauling one country’s officials in front of the judges and juries of another.

Alas, the Senate and the House have unanimously voted to weaken this principle in the noble-sounding cause of justice for American victims of alleged state-sponsored acts of terrorism. The legislation, sparked by much-ballyhooed but so-far-unsubstantiated claims of official Saudi collusion in the Sept. 11, 2001, attacks, would permit victims of acts of terrorism in the United States to sue alleged state sponsors for monetary damages in federal court. Under current law, such suits are permissible only against governments that the State Department has already designated as sponsors of terrorism: Iran, Syria and Sudan. The bill would enable private individuals and their lawyers to add oil-rich Saudi Arabia, perhaps the ultimate deep-pocketed defendant, to that list. Someday, other countries could find themselves in the dock, too.

Proponents describe the bill as a “narrow” adjustment to existing law, and, to be sure, they have watered down more sweeping earlier versions in the face of veto threats from President Obama and criticism from international-law and national-security experts. The revised bill allows the executive branch to freeze any given suit for 180 days, by certifying to a court that it is engaged in good-faith negotiations to resolve the plaintiff’s claims with the defendant nation. Such a stay could be extended for as long as the State Department certifies that the negotiations are still ongoing. As long as an administration is willing to jump through these hoops, it could probably block an objectionable lawsuit indefinitely, which makes one wonder what the point of the bill is anymore.

Note, however, that this would require the executive branch to conduct negotiations so it could make the certification, even if it didn’t think such talks were warranted. And the bill leaves it up to a court whether to grant the initial stay. This is still too much power to give unelected, inexpert judges over a core function of the political branches.

In short, to the extent the revised bill isn’t merely symbolic, it’s mischievous. Mr. Obama has repeatedly called it a precedent other countries could easily turn against the United States. It is not a far-fetched concern, given this country’s global use of intelligence agents, Special Operations forces and drones, all of which could be construed as state-sponsored “terrorism” when convenient. Even if a future administration did succeed in blocking a lawsuit, the mere filing of it could irritate the target country or countries. Members of Congress have repeatedly claimed enough votes to override Mr. Obama’s veto threat, and they may be right. Mr. Obama should carry it out anyway. If long-standing principles of law and policy are to be discarded so lightly, at least let it be done without his approval.