By DAVID ROHDE, The New York Times

The arrest of Radovan Karadzic on Monday gave badly needed credibility to international war crimes tribunals that have struggled for years to bring fugitives to justice, according to former prosecutors, legal experts and human rights groups. And the arrest bolstered arguments from tribunal officials that patience, multilateral diplomacy and creativity can make the institutions more effective.

“It’s building up piece by piece,” said Martha Minow, a law professor at Harvard and an expert on war crimes trials. “This is building up the legitimacy of these institutions.”

Mr. Karadzic will be the third high-profile figure to be brought before a United Nations-backed tribunal on war crimes charges in the last six years, following in the footsteps of President Charles Taylor of Liberia and the Serbian president, Slobodan Milosevic. For years, supporters of the tribunals have argued that if leaders were brought to trial the courts could serve as a deterrent.

But Mr. Karadzic, who remained free for nearly 13 years, made a mockery of the International Criminal Tribunal for the Former Yugoslavia, which in 1983 became the first such body established by the United Nations.

Although repeatedly seen in public when American and NATO forces entered Bosnia in 1996, he was not arrested, in part out of fear that seizing him could cause a violent backlash against NATO forces.

Instead, the United States and the European Union tried to use economic and diplomatic pressure on Serbia to force his arrest. Until Monday, the policy appeared to be a failure.

At the same time, other war crimes tribunals established by the United Nations came under fire. The International Criminal Tribunal for Rwanda was criticized by Rwandans as being hugely expensive, based outside Rwanda and largely detached from the country itself. And the establishment of the International Criminal Court — a permanent tribunal intended to prosecute war crimes globally — was delayed for years by tortuous negotiations and fierce opposition from the Bush administration.

Only last week, the prosecutor of the International Criminal Court was criticized for requesting that genocide charges be filed against President Omar al- Bashir of Sudan. Critics warned that the move would complicate peace negotiations for the Darfur region of Sudan and never lead to Mr. Bashir’s arrest, given the international community’s poor track record on arresting fugitives.

After Mr. Karadzic’s s arrest, legal experts said his capture bring subtle new pressure to bear on the Sudanese leader.

“When Karadzic was indicted back in 1995, nobody really expected he’d ever actually get arrested,” said Gary Bass, a professor of politics and international affairs at Princeton University and the author of “Stay the Hand of Vengeance: The Politics of War Crimes Tribunals.” “It’s not clear how exactly Bashir could wind up in The Hague,” he added, “but the Karadzic example has got to make Bashir think hard.”

Privately, officials from the war crimes tribunals have argued that the United States and its allies have lacked the political will to make arrests and at the same time failed to use a complex array of diplomatic and economic measures to bring fugitives to justice. The international community has more options than either using military force to arrest a fugitive or doing nothing, they say. Economic sanctions, indictments and travel restrictions all place small but steady pressure on individuals accused of war crimes and on their patrons.

Undermining a leader’s or regime’s legitimacy can also serve as leverage.

“The third way is what the world needs,” said one war crimes investigator who spoke on condition of anonymity. “The problem is we are thinking two ways: we accept him or we go to war with him.”

Critics point out that the tribunals’ track records have, until now, been poor. Mr. Karadzic’s arrest now does not make up for more than a decade of successful defiance. The amount of time it took to pressure Serbia to arrest Mr. Karadzic shows how easy it is for states to defy and divide the international community.

For years, many of survivors of the 1995 massacres in Srebrenica — for which Mr. Karadzic was indicted on genocide charges — mocked the Yugoslavia tribunal as a toothless and expensive show put on by the international community. They said the court, which is based in the Netherlands and has an annual budget of $150 million, would remain a multimillion-dollar failure until Mr. Karadzic and his military commander and co-defendant, Gen. Ratko Mladic, were arrested.

Richard Goldstone, a South African jurist who served as the Yugoslavia tribunal’s first chief prosecutor and indicted Mr. Karadzic in 1995, said it was critical that Serbian officials also arrest General Mladic, who remains free and is believed to be hiding in Serbia as well. “I just hope that Mladic is not that far behind,” he said.

Human rights groups said the arrest of Mr. Karadzic had the potential to significantly bolster the clout of the long-maligned tribunals. Richard Dicker, director of Human Rights Watch’s International Justice Program, said that Mr. Karadzic had come to “personify impunity.”

“For international justice, this is a very good thing,” he said. “ I think it validates that justice has a long memory and a long reach.”