The new secretary-general of the United Nations, Ban Ki-moon, says his “first priority will be to restore trust” in the world body. It is a slap at the outgoing secretary-general, Kofi Annan, who did so much to erode that trust. Mr. Ban appears to realize that his accession comes at a juncture when the hopes invested in the United Nations have dimmed. Example after example has demonstrated that individual sovereign countries, or alliances among them, are more effective than the United Nations.

Only this week brought news of the death of Augusto Pinochet of Chile, who died before he could be brought to justice in an effort that included both Spanish and British courts. Slobodan Milosevic, too, died before the U.N.’s unwieldy International Criminal Tribunal for the Former Yugoslavia could conclude its case against him. Ethiopia’s own courts this week did manage to convict the man who served as the country’s Marxist dictator, Mengistu Haile Mariam, of genocide. He is still alive but in exile. We think, too, of Iraq, when the United Nations flinched at ousting Saddam, but America and its allies went forward and liberated the country.

Yet the hope in international law and international institutions persists, notwithstanding the weight of the evidence. That hope was on display in New York this week not only in Mr. Ban’s opening remarks but also at a parley convened by the Conference of Presidents of Major American Jewish Organizations on the prospect of bringing the president of Iran, Mahmoud Ahmadinejad, to justice for violating the 1948 Convention on the Prevention and Punishment of the Crime of Genocide. That meeting included America’s ambassador at the United Nations, John Bolton, who spoke in support of the effort, as well as a former Israeli ambassador at the United Nations, Dore Gold. Whether that effort gets anywhere at the United Nations will be a good way to measure whether Mr. Ban is making any progress in restoring trust.