In the past two decades, experts monitoring the international arms trade recorded more than 500 violations of United Nations arms embargoes. Just two have resulted in trials and convictions.

This telling statistic helps explain why diplomats, experts and arms control activists are in New York this month at a U.N.-hosted conference aimed at working out a treaty to regulate a vast market that so far has fewer rules than the trade in bananas. Where high reward-low risk activities are concerned, few can match the international arms trade, licit or illicit.

The contrast between the number of embargo violations and the number of arms dealers held to account comes from a study, to be published later this year, conducted by a team led by James Stewart, a law professor at Canada’s University of British Columbia in Vancouver. Stewart looked into cases, dating back to 1990, that prompted U.N. panels of experts to report violations of embargoes imposed by the U.N. Security Council.

“Despite extensive searches, we couldn’t find more than two convictions,” said Stewart, who worked as a prosecutor for the International Criminal Tribunal for the former Yugoslavia before joining academia. What were the two cases that broke the pattern of impunity for embargo busters?

In 2007, a court in The Hague sentenced Dutch businessman Frans Van Anraat to 17 years in jail for selling raw materials for the production of mustard gas to the government of Saddam Hussein. Last January, Chile’s Supreme Court convicted two retired generals and seven others of illegally exporting weapons to Croatia in 1991. The case reached the country’s highest court after a long march through the military justice system.