The Islamic State’s campaign of religious and cultural cleansing has shocked the world and terrified the peoples of Iraq and Syria who don’t fit into the group’s fanatical vision of a neo-Islamist caliphate. At a meeting last Friday at the United Nations, the French foreign minister, Laurent Fabius, made a fresh appeal to the Security Council to refer the Islamic State to the International Criminal Court, or I.C.C., for possible prosecution for crimes against humanity, war crimes and, Mr. Fabius suggested, cultural genocide.

There is broad international consensus that the Islamic State deserves to face judgment for its crimes. Beyond the slick videos gleefully documenting beheadings and the burning alive of a Jordanian Air Force pilot, the Islamic State has sought to purge ethnic and religious minorities, including Yazidis, Turkmen, Shabaks, Sabaeans and Shiite communities from their age-old homelands. A chilling report released on March 19 by the United Nations Human Rights Council — also urging the Security Council to refer the Islamic State to the I.C.C. — documents a litany of serious crimes, including executions, rapes, forced conversions, torture and enslavement, as well as the systematic destruction of churches, shrines and mosques. The report said the Islamic State’s intent to destroy the Yazidis as a group “strongly suggests” it may be guilty of genocide.

Despite the overwhelming evidence of crimes of the highest order, it is far from certain that the Security Council will act. Last May, China and Russia effectively vetoed a Security Council resolution to refer war crimes committed under the regime of President Bashar al-Assad of Syria to the I.C.C. As of the end of last year, an estimated 206,603 Syrians had died in the country’s four-year civil war, including 3,500 children in 2014 alone. More than 15 million Syrians have been forced to flee their homes.

But the reality is that Mr. Assad has become a necessary, if still unpalatable, potential ally in combating the Islamic State. The Security Council could partly redeem its failure to protect minorities and other civilians in Syria and in Iraq by tackling the shameful impunity of the Islamic State, and refer the group to the I.C.C.