It was as classic a sting operation as any on Manhattan’s streets: a government cooperator offered a fictitious deal, and baited a suspect into agreeing to participate in illegal activity.

But in this instance, the target was Viktor Bout, a reputed arms trafficker who lived in Moscow; the purported deal involved selling arms to Colombian terrorists; and the sting involved meetings in the Netherlands Antilles, Romania, Denmark and, finally, Thailand, where Mr. Bout was arrested and then extradited to the United States.

The case of Mr. Bout illustrates the expanded global reach of the office of the United States attorney for the Southern District of New York. Since 2004, the office has sent prosecutors into more than 25 countries as part of investigations
that have brought back dozens of suspected arms and narcotics traffickers and terrorists to Manhattan to face charges. With the United States Drug Enforcement Administration, the office has also taken the lead in bringing cases under a 2006 narco-terrorism law that makes it easier to prosecute global drug traffickers if a link to terrorism can be shown - even if prosecutors cannot prove that the drugs entered the United States.

Federal prosecutors elsewhere pursue cases abroad, but not in such numbers , the evidence suggests.

Defense lawyers have criticized the stings, arguing in court that they “manufacture jurisdiction” in cases in which it would not otherwise exist and pursue people unfairly.

Countries have not always rushed to cooperate, as in the 2010 extradition of the reputed Jamaican drug lord Christopher Coke, a review of secret State Department cables released by WikiLeaks shows.

“I find it profoundly troubling that U.S. agents are spending their time setting up cases against individuals who do not represent actual threats to the United States,” said Melinda Sarafa, a lawyer for a Lebanese man brought from Honduras in a 2009 narco- terrorism sting.

A Jamaican official predicted that if the government arrested Mr. Coke, who exerted extraordinary power in his stronghold, there could be “severe repercussions.”
There were more than 70 deaths before his arrest in June.

Sabrina Shroff, a lawyer for a West African narcotics-trafficking suspect , said, “It would anger our citizens if Americans were set up, and ensnared, and tried in a foreign country.”

In the stings, paid D.E.A. informers have posed as representatives of terrorist groups, like the Taliban or the Revolutionary Armed Forces of Colombia, or FARC. The informers are typically sent to approach suspected arms or drug traffickers , and propose conspiracies that include acts against Americans.

The creation of a global narcotics unit around 2002, at the suggestion of a prosecutor, Richard J. Sullivan, now a federal judge, was key to expanding the office’s vision. Besides the FARC and the A.U.C., a right-wing Colombian paramilitary group, the unit focused on powerful drug organizations in Mexico, Asia, Europe and the Middle East.

“ We needed to dismantle entire organizations, not just the U.S.-based cells,” Judge Sullivan recalled, “and that the only way to do that was to apply organized- crime-fighting methods .”

In 2008, the office won the convictions of a prominent Afghan tribal leader, Haji Bashir Noorzai, for drug-trafficking conspiracy, and a Syrian arms dealer, Monzer al-Kassar, on charges of conspiring to provide material support to terrorists and to kill Americans.

Cases that come to New York do not have to have a connection to the city, as long as there is an impact on the United States. In 2010, for example, the office won the conviction of a Pakistani scientist who tried to kill American officers and agents in Afghanistan.

The Southern District has brought five cases under the 2006 narco-terrorism law.

Juan C. Zarate, now at the Center for Strategic and International Studies, said the Southern District’s approach was “cutting edge” because of the new ways terrorist and narcotics groups were working together abroad.

He also noted that suspected arms dealers like Mr. Bout, who was ensconced in Moscow, and Mr. Kassar, who lived in a mansion in Marbella, Spain, had for years seemed almost untouchable, legally and physically.

Preet Bharara, the United States attorney for the Southern District, said the aggressive approach had become necessary in the post-9/11 era. “As crime has gone global ,” he said, “in my view the long arm of the law has to get even longer. We can’t wait until bombs are going off.”


By BENJAMIN WEISER