Former United Nations weapons inspector Hans Blix said world leaders must think critically before launching a war, during a lecture in Luce Hall on Monday in which he criticized the Bush administration’s military action in Iraq.

Speaking to a group of more than 250 students and faculty in the crowded auditorium, Blix described his experience as leader of the 2002-’03 UN investigation into Iraq’s suspected arms buildup and weighed in on the current debate over an appropriate international response to the threat of large-scale weapons proliferation. Taking examples of the successes and failures of the UN’s disarmament efforts — ranging from the neutralization of South Africa’s nuclear program to India’s continued insistence on maintaining its weapons infrastructure — Blix outlined his goals for the future of these efforts and said he hopes the United States will set an example by disarming.

As head of the United Nations Monitoring, Verification and Inspection Commission, Blix delivered the commission’s final verdict in February 2003 that contrary to the claims of the United States and Great Britain, no weapons of mass destruction were found in Iraq.

In spite of this conclusion, Blix said on Monday, the United States still chose to invade Iraq in a preemptive assault predicated on the assumed existence and danger of these weapons.

“The war in Iraq in 2003 was not justified,” Blix said. “After the Iraq war, we know that [incomplete intelligence] can be a very shaky basis.”

Blix said the commission’s findings, while not conclusive in disproving the existence of weapons in Iraq, did not offer any evidence indicating the presence of weapons or suggesting that Saddam Hussein planned to use such weapons against other countries.

Even the most advanced inspection capabilities may be inadequate in the face of constantly increasing hostile technologies such as the anthrax engineered during the brief bioterrorism scare in 2001, Blix said. The UN Commission’s primary goal is to ensure that weapons are not made by “states, terrorists and mad scientists,” he said.

“The confidence that nuclear weapons will not be used will only come from knowing that they do not exist,” Blix said.

Blix began his lengthy political career in the Swedish government, serving in Sweden’s delegation to the UN from 1961 to 1981 and as the country’s foreign minister in the late 1970s. He then headed up the International Atomic Energy Agency from 1981 to 1997, at which point he retired only to be called back to duty by UN Secretary-General Kofi Annan in 2002 to conduct the Iraq inspections. Since then, his 2004 book “Disarming Iraq” has revealed to the international community his many reservations about the war’s rationale.

But Blix has been criticized by a number of U.S. politicians for his alleged weaknesses in mandating Iraq’s compliance with weapons inspections. In particular, his detractors point to Iraq’s ability to conceal its 1980s uranium enrichment programs from Blix and the IAEA. When Blix was chosen to reprise his investigatory role in 2002, critics in Washington, D.C., claimed that his cautious approach and the cultural sensitivity workshops in which his staff participated were signs that Blix would not be aggressive enough to push Hussein into revealing weapons program plans.

Despite these criticisms, Blix said he stands by the integrity of his investigation, stating that his commission performed 700 investigations at 500 separate sites, including several that had been recommended by U.S. intelligence. Blix said the international community today should emphasize collaboration in disarmament and that individual countries — particularly the United States — should set an example by dismantling their weapons programs.

“There is a crying need for revival of global disarmament efforts and respect for the UN,” Blix said.

Students at the lecture said they appreciated hearing the perspective of a diplomat who had seen firsthand the inspection sites in Iraq and who was at the forefront of the nuclear nonproliferation debate.

“He made a strong case that international inspection was far preferable to unilateral action and intelligence,” Raffi Magarik ’10 said.

But Shane Deighton ’10 said he thought Blix was not candid enough about criticisms directed at the United Nations — especially concerning the scandal surrounding the UN’s oil-for-food program.

“I’m a little dubious about his comments that there’s no corruption in the UN,” Deighton said. “I was disappointed about the glossing over of that issue.”

Other students said they were impressed by Blix’s calm discussion of an issue that usually inspires much passion and fiery rhetoric.

“I think it was very elucidating as to the political situation in the Middle East,” Benjamin Miller ’10 said. “He definitely brought a more reasonable set of arguments to a debate that is usually very highly charged.”