A DOZEN years after its creation, the International Criminal Court is foundering. So far it has brought just 21 cases in eight countries, all of them in Africa. Only two have resulted in convictions — of relatively obscure Congolese rebel leaders. Though 139 countries signed the founding treaty, the United States, Russia, China, India, Israel and every Arab nation but Jordan have declined to join. The most horrific crimes against humanity perpetrated in the world in the past decade — in North Korea, Syria and Sri Lanka, among other places — remain outside the ICC’s reach.

Worse, in two big cases the court bet that it could bring current heads of national governments to trial — and lost. This month the court’s chief prosecutor was forced to abandon a case against Kenyan President Uhuru Kenyatta, who had been charged with orchestrating a 2007 campaign of ethnic violence. Though Kenya is a member of the court, the government refused to cooperate with the prosecution, making it impossible to gather sufficient evidence.

That embarrassment is matched by the court’s failed 2008 indictment of Sudanese President Omar al-Bashir on charges of war crimes and crimes against humanity. An ICC warrant for Mr. Bashir’s arrest was issued in 2009, but not only does he remain president of Sudan but he also has traveled to Egypt and Qatar with impunity. A week after the Kenya decision, the ICC prosecutor suspended evidence-gathering in the Darfur region where the crimes occurred.

The court’s purpose was to prevent the world’s worst war and human rights crimes from going unpunished, both for the sake of justice and to deter future atrocities. But the guilty escaped sanction, and the court’s deterrence effect is looking weak. Even Congo’s warring factions continue to commit horrific crimes.

The record suggests the court lacks the clout to pursue cases in places where regimes remain in place and conflicts are unresolved. Its jurisdiction began only in 2002 , so it cannot pursue crimes committed long ago. What remains to be seen is whether it could be more successful in helping to prosecute offenses after wars end and political transitions are completed. An international settlement on Syria following the departure of the Assad regime, for example, could and should include a referral of crimes to the ICC.

Pending such opportunities, the court may be tempted to pursue more quixotic initiatives. This month chief prosecutor Fatou Bensouda reported that she was “assessing available information” on “enhanced interrogation techniques” by U.S. forces in Afghanistan, which is an ICC member. This month’s Senate Intelligence Committee report on cases of torture may increase the impetus behind that probe. But the alleged crimes committed by U.S. personnel, though shocking, are not grave enough to meet the ICC’s high bar for prosecution — and it would be politically foolish for the court to pursue U.S. targets.

Similarly, Ms. Bensouda will be put on the spot if the Palestinian Authority elects to accede to the ICC treaty and bring charges against Israel for its actions in the West Bank and Gaza Strip. In that case the court would be theoretically obligated to simultaneously investigate crimes by Hamas and other Palestinian groups, but might find it practically as well as politically easier to zero in on Israel. That, too, would be an error that could destroy the ICC’s chances of gaining international credibility.