The House of Representatives is currently considering legislation passed by the Senate that would change the law of foreign sovereign immunity in order to allow the families of victims of the 9/11 attacks to sue Saudi Arabia, where 15 of the 19 attackers were citizens, for its supposed culpability. Setting aside for a moment whether Saudi Arabia did have any contact with the terrorists—and it has vehemently denied that it does—the bill raises both policy and practical concerns. Congress should think carefully about the downsides of the legislation before enacting it, but if it does feel compelled to change the law, it should make sure that the real beneficiaries are the families of the victims and not their lawyers.

Foreign sovereign immunity is a doctrine that ensures that diplomatic disputes are resolved between national governments rather than in the courts. American courts have traditionally been very wary about impinging on the power of the other branches of the government to conduct foreign policy, and the United States gives foreign countries immunity from suit in the United States in order to ensure reciprocal treatment in foreign countries. The U.S. government does not want to find itself a defendant in foreign countries whenever the citizens of that country have a grievance arising out of U.S. foreign policy.

If Congress were to adopt legislation that pares back sovereign immunity for Saudi Arabia or any other countries, it should expect other countries to do likewise. Suddenly, the U.S. might find itself defending against claims by individuals in other countries who accuse the U.S. of engaging in what they define as acts of "terror." This could include lawsuits in Pakistan or Yemen by families of victims of drone strikes, lawsuits in Syria by families of victims of airstrikes, or even lawsuits in Turkey by someone who claims that the U.S. has "harbored" Fethullah Gulen. The U.S. could also find that its soldiers, diplomats, and other personnel face liability for actions of the U.S. government.

It goes without saying that such legislation would strain American relations with Saudi Arabia and, potentially, many other countries as well.

Beyond the policy concerns, the legislation now before Congress presents practical problems as well. American litigation includes a broad right to discovery. That means that parties to a lawsuit can collect information both from their opponents and from third parties that might have relevant information. In lawsuits about acts of terror, such information will often appear in confidential or classified government information, including diplomatic cables and intelligence files. For example, in the case of the 9/11 hijackers, questions might arise about what the United States knew about them and what it told the Saudis about them. In mounting a defense, Saudi Arabia would likely seek this intelligence from the United States by way of a subpoena. By passing this law, Congress would be opening the door to discovery of sensitive American information. At a minimum, it will be forcing the government into contentious battles to preserve the secrecy of American information.

Another practical problem with any litigation is ensuring that the parties intended to benefit—the families of the victims—will in fact be the ones who will receive the bulk of any money paid out. There were thousands of victims on 9/11, and while many of the lawyers representing them might do so on a pro bono basis, not to mention a sincere desire to see them made whole, better prospects at recovery would doubtless attract more mercenary contingency-fee lawyers, who would seek a substantial percentage of any recovery. If Congress passes legislation that ends over two centuries of established law and damages political alliances throughout the globe, the net result should be something more than making a handful of trial lawyers obscenely rich.

The solution is simple: If the House does move the Senate legislation forward, it should include provisions to cap the amount that the lawyers can receive. For example, it could include a provision to cap the amount the lawyers receive at a small percentage of total settlements, say 5 or 10 percent. Or it could also acknowledge that lawyers pursuing cases on a contingency take on a certain amount of risk and limit the lawyers to no more than two or three times the cost of their actual investment in the case. With either proviso the money available would be still be ample enough to compensate lawyers without making the act a windfall for them.

If Congress really cares about the families of victims of 9/11, it will take steps to ensure that its legislation protects those families in a meaningful way.

Joshua Wolson is a partner with Dilworth Paxson in Philadelphia. Ike Brannon is president of Capital Policy Analytics, a consulting firm in Washington.