The International Criminal Court was created in 2002 with an audacious promise: to go after the biggest perpetrators of crimes against humanity, and those who commit genocide.

But so far, it seems, the arm of international law has been able to reach only those who have few powerful friends to protect them.

The case against Sudan’s president, Omar Hassan al-Bashir starkly illustrates the court’s profound limitations, and the reason it is such a lightning rod.

The court can indict even sitting heads of state, as it did with al-Bashir. But it has no power to handcuff them and put them in the dock. Instead, the court relies on other heads of state and governments to act as its sheriffs around the world, and for the last six years, many of them have let al-Bashir flout the court’s arrest warrant.

Monday was a case in point. South Africa let al-Bashir fly home despite an order from South Africa’s High Court instructing the nation’s authorities to prevent him from leaving the country.

Given its constraints, said Alex Whiting, a former attorney with the ICC prosecutor’s office and now a law professor at Harvard, the International Criminal Court "will only be as relevant as the international community allows it to be."

South Africa was merely the most recent country to let al-Bashir visit and leave without arrest. It was a reminder, Whiting argued, of how hard the court must work to overcome the perception that it is targeting only Africans — and a reminder of how justice cannot be meted out unless the world powers invest in it.

"Bashir will ultimately be arrested," he said, "only if the Security Council and countries like the U.S. and other important actors undertake a sustained effort to prioritize his arrest and make it a central part of their diplomatic efforts."

But while the United States can pressure other nations to act, it faces a major credibility problem of its own. Unlike dozens of African nations, some of the world’s most powerful countries, including the United States, Russia and China, have not even joined the International Criminal Court, officially refusing to submit to its authority.

In 2011, al-Bashir visited China, where he was greeted by an honor guard and he met with China’s president at the time, Hu Jintao. Al-Bashir called him "a friend and brother."

Mark Ellis, president of the International Bar Association, said the latest al-Bashir drama further weakened the authority of the court, through no fault of its own.

It was set up in such a way that the world’s most powerful countries were able to keep themselves — and often their allies — out of its reach. That, he said, has allowed African leaders to assert that they have been unfairly and disproportionately targeted by the court.

"The International Criminal Court is weakened because major political powers have not embraced the court," Ellis said.

International justice, he added, cannot mean "a system where states are able to say, ‘I’m going to withdraw from any accountability because I’m not going to engage in this process.’"

The court has issued 30 arrest warrants but won only two convictions. Many, like al-Bashir, have eluded arrest.

The U.N. Security Council referred the crisis in Darfur, Sudan, to the international court in 2005, leading the prosecutor to indict al-Bashir on charges of war crimes, crimes against humanity and genocide.

In the years since, the Security Council has done little to help the court get hold of him, even after he traveled to countries like Kenya, Chad and Nigeria, evading arrest.

Chad and Nigeria, both U.S. allies, were elected as temporary members of the Security Council. Al-Bashir’s powerful allies, China and Russia, are permanent, veto-wielding members of the Security Council.

The court has secured the arrests of lesser-known figures, most recently a man it had all but given up on: Dominic Ongwen, a Ugandan rebel commander who is charged with a long list of war crimes.

It is also prosecuting a former head of state from Ivory Coast, Laurent Gbagbo, and says the trial of Bosco Ntaganda, a rebel leader charged with war crimes in the Democratic Republic of Congo, is scheduled to start in mid-July.

Other international tribunals, separate from the international court, have convicted top leaders implicated in war crimes in Rwanda, Sierra Leone and the former Yugoslavia.

Still, the court has become a major point of international contention, in large part because world powers have used it selectively to advance their own interests.

Last year, France sought to persuade the Security Council to refer the situation in Syria to the court — a bid that was backed by the United States but vetoed, as expected, by Russia, an ally of the Syrian government.

The Palestinians have used the court to advance their cause. They joined the court in December as part of their effort to pursue statehood in the international arena after decades of failed negotiations with Israel. France, usually an enthusiastic supporter of the court, publicly said nothing in support of the Palestinian decision, while the United States was unequivocally critical.

The court’s reputation for neutrality came under attack after it indicted two African heads of state — al-Bashir and his counterpart in Kenya, Uhuru Kenyatta — in connection with the violence that swept his country after the 2007 elections.

The court was accused of bias against Africa, a charge that its chief prosecutor, Fatou Bensouda, a Gambian, has forcefully denied.

Still, the African Union pledged not to cooperate with the court on cases against sitting heads of state. In December, Bensouda announced she would drop the charges against Kenyatta, citing his government’s lack of cooperation. That month, she also said she would "hibernate" the genocide case against al-Bashir, blaming the Security Council for not helping her secure his arrest.

The court has been looking beyond Africa in recent years. Bensouda has opened a preliminary examination into the role of British soldiers in Iraq. She has said she is looking into allegations of torture by U.S. soldiers in Afghanistan, though she is far from opening an official investigation.

The Palestinian issue is by far the trickiest. The prosecutor must decide whether to investigate allegations of war crimes committed by Palestinians or Israelis during the 2014 Gaza war, the expansion of Israeli settlements or both issues.

Israel seems to be taking the possibility of an investigation by the court seriously, said Diane Orentlicher, a professor of international law at American University. The Israeli authorities have issued a barrage of legal opinions to defend their conduct during the 50-day war in Gaza last summer, even before the prosecutor has announced an official investigation.

As for South Africa, its government ended up flouting its own courts as well as the International Criminal Court, she said.

"And while the ICC once again faces a state party’s refusal to arrest a suspect to be sure, this episode also reminds us that the court has an enduring impact on Bashir’s ability to function as a member of the global community," she said in an email. "After all, he did not leave South Africa on his preferred terms."

Even so, some analysts said South Africa’s decision to let al-Bashir leave could empower other nations — like Israel, which has not endorsed the court — to be uncooperative.

"Having a prominent state party and proponent of the court like South Africa, which is under a duty to comply, refuse to do so would only strengthen Israel’s position," said Eugene Kontorovich, a law professor at Northwestern University.