When Congress returns from summer break this week, it will face enormous pressure to pass the Justice Against Sponsors of Terrorism Act. Although enticingly named, Jasta is far more likely to harm the United States than bring justice against any sponsor of terrorism. Counterterrorism policy in the past eight years has been a failure, but this bill won’t fix it.

Jasta would create an exception to sovereign immunity, the legal doctrine protecting foreign countries and their diplomatic personnel from suit in U.S. courts, if a...