JOHANNESBURG — It was exactly the kind of case the International Criminal Court was created to investigate: Yemen’s autocratic leader was clinging to power, turning his security forces’ guns on unarmed protesters. Hundreds were left dead, and many more were maimed.

But when Yemen’s Nobel laureate, Tawakkol Karman, traveled to The Hague to ask prosecutors to investigate, she was told the court would first need the approval of the United Nations Security Council. That never happened, and today the former president, Ali Abdullah Saleh, is living comfortably in Yemen’s capital, still wielding influence.

Now, as the world confronts increasing evidence of atrocities on a much vaster scale in Syria as President Bashar al-Assad’s government battles a growing rebellion, there are signs that Mr. Assad is likely to evade prosecution, much as Mr. Saleh has.

The men have not been prosecuted because they have powerful allies, underlining what critics say are crucial flaws in the court’s setup. That now threatens to undermine the still-fragile international consensus that formed the basis for the court’s creation in 2002: that leaders should be held accountable for crimes against their own people.

Already, the failure to act against some leaders challenged by the Arab Spring is emboldening critics who see the court as just another manifestation of a deeply undemocratic international order. So-called justice, they say, is reserved for outcast leaders, including an assortment of African officials from weak states with few powerful patrons.

“We have the feeling that international justice is not ruled by law,” said Rami Nakhla, an exiled Syrian activist and member of the Syrian National Council, an opposition group. “It is ruled by politics, it is ruled by circumstances. It depends on the situation, it depends how valuable this person is. That is not real justice.”

Since it was created, the International Criminal Court has signed up 120 member states, including many nations that perpetrated or suffered some of the 20th century’s gravest atrocities: Germany, Poland, Japan, Cambodia, the Democratic Republic of Congo, Sierra Leone, Argentina and Colombia. The long-held dream of a court with universal jurisdiction that could prosecute crimes against humanity committed anywhere is today closer than ever to being a reality.

Three former heads of state are in custody of international courts, and one, Charles Taylor, has been convicted of war crimes. The International Criminal Court has opened multiple investigations in some of the last decade’s worst conflagrations, and convicted one defendant, a Congolese warlord who turned young boys into killers. The trial of a former Bosnian Serb general, Ratko Mladic, is scheduled to resume Monday at the tribunal created to try accused war criminals from the former Yugoslavia.

The International Criminal Court was meant to replace the ad hoc courts created for a single conflict like Sierra Leone and Yugoslavia with a tribunal with global reach to investigate continuing atrocities. But the court does not have truly universal jurisdiction. It can investigate crimes only in nations that have signed the Rome Statute, which created the court, unless the Security Council refers a case.

In the Middle East, where few nations have signed and many have strong allies on the Security Council, authoritarian leaders can proceed with impunity. That threatens to undermine confidence in the entire system.

“So many crimes have been committed here,” said Nabeel Rajab, a rights activist in Bahrain, where the royal family, with help from Saudi Arabia and the acquiescence of the United States, has used force to put down a pro-democracy uprising. “But because of the close relationship between Western powers and the government of Bahrain, how can we hope for justice?”

The International Criminal Court began working a decade ago with very low expectations and little support from the major world powers. Three of the five veto-holding members of the Security Council — the United States, Russia and China — refused to subject themselves to its jurisdiction. Despite this, it has turned into a touchstone for justice-seekers so powerful that The Hague has become their desired destination for autocrats everywhere. The Security Council allowed the court to investigate Sudan’s president, Omar Hassan al-Bashir, who ended up being indicted on charges of war crimes in Darfur, though the court has been unable to apprehend him.

And in February 2011, the Security Council voted unanimously to ask the International Criminal Court to investigate the Libyan government led by Colonel Muammar el-Qaddafi. The court handed down indictments against Colonel Qaddafi and several top officials, though he was killed in Libya before he could face prosecution.

But the court has not taken action in any other Arab uprising, in no small part because of the ties between the countries involved and veto-holding members of the Security Council. Bahrain and Yemen are allies of the United States, which is not a signatory to the International Criminal Court. Russia and China, neither of which is a signatory, are close to Syria’s government, and are likely to block any attempt to refer a case to the court.

“Is Syria the kind of situation that should get the court’s attention? Absolutely,” said Kevin Jon Heller, a leading scholar of international justice and an international defense lawyer who teaches at the University of Melbourne in Australia. “But there is an inherent selectivity. As long as any country has a patron on the P5,” he said, referring to the veto-holding members of the Security Council, “it will never get referred.”

For years African countries have complained that the International Criminal Court has focused exclusively on African conflicts. In some ways this was unintentional: the court can investigate only atrocities committed after its creation in 2002, and in that period many of the bloodiest conflicts in the court’s jurisdiction have taken place in Africa.

But the African focus shows how tricky the jurisdictional questions are. Much of Africa has ratified the Rome Statute, with notable exceptions like Sudan, Ethiopia and Zimbabwe. In some instances, governments in Africa have referred cases involving rebel groups on their own territory, as in Uganda and the Central African Republic. In others, like the postelection violence in Kenya in 2008, the office of the International Criminal Court prosecutor has used its power to open investigations.

But other situations have escaped the court’s reach. At the bloody end of the civil war in Sri Lanka in 2009, 200,000 civilians were trapped on a beach between government forces and the Tamil Tigers. Tens of thousands are believed to have been killed, but the International Criminal Court has never investigated the case. Sri Lanka is a close ally of China. Charges of crimes in Gaza will never be investigated, international justice experts say, because of the ties between the United States and Israel.

The United States never agreed to be subject to the International Criminal Court because of constitutional issues and worries that its citizens, especially soldiers and spies, could be brought before the tribunal. This is no idle fear, given the human rights scandals that have exploded in Iraq and Afghanistan involving United States personnel. Other countries have rejected it as an unacceptable infringement on their sovereignty.

International justice is also slow and expensive, leading some to question whether it is really worth it. The International Criminal Tribunal for the former Yugoslavia was created in 1993, and it is not expected to wrap up its work until 2014. The Special Court for Sierra Leone, which convicted Mr. Taylor, was created in 2002 and has cost hundreds of millions of dollars, leading many people in that impoverished country to wonder whether the money could have been better spent on development.

Debates have raged for years about whether the court, by closing off a graceful exit, makes dictators more likely to fight to the death. Some question whether it is an effective deterrent of war crimes. The court has run into another problem in Libya: the new government seems intent on prosecuting surviving members of the old leadership itself despite deep concerns about the ability to hold fair trials.

Supporters of the court say it has achieved far more than anyone expected when it was created. “The assumption was the court will take years to come into effect,” said Darryl Robinson, a law professor at Queen’s University in Canada who worked as an adviser to the International Criminal Court’s prosecutor. “And once it is in force it is going to be this court with jurisdiction over Canada and Norway, with nothing to investigate.”

Instead, much of the world has signed up, and protesters in Yemen, Bahrain, Libya and Syria have demanded that their leaders be sent to The Hague for trial, testimony to the court’s wide resonance. The deeper question is whether the failure to prosecute the autocrats of the Arab Spring will erode faith in the movement toward a truly universal system of international justice.

“For justice to be legitimate, it is essential that it be applied equally to all,” said Richard Dicker of Human Rights Watch. “Justice has advanced, and in doing so, the flaws that mark it in today’s world become more apparent. The double standard must change for the whole undertaking to retain its legitimacy.” (Copyright 2012 The New York Times Company 07/08/12)