IIRC, the guy was smuggling .50 BMG rifles to the Bosnian Muslims.
As much as anybody could be considered the good guys/victims in that little cesspool, the Bosnian Muslims were it. And like most U.N. arms embargos, it just left the defenders short handed against the agressors, and vulnurable to genocide. The Bosnian Serbs who were making a push for ethnic cleansing in the area had much larger supplies of post-Soviet arms at their disposal, and backing from larger Serbian areas.
And because so much of the warfare in the former Yugoslavia, and it's successor states was siege style, covering the cities from the surrounding mountainsides, and shelling and siping them to death, high-caliber sniper rifles were uniquely suited to the conflict. A rifle that could reach up into the mountains and hit artillery emplacments, or even just make them keep their heads down, or decide to relocate, would be very useful.
The larger issue (besides trying to knock American gun owners/businesses) was that because of the larger regional Muslim affiliations with the Bosnian Muslims, such as Chechnya, Iran, and Afghanistan, there was concern that the .50 cals may have made their way to the Chechen seperatist movment, or to AlQueida themselves.
Frankly, without the proper training, and a steady supply of .50 match grade ammo, I don't think those .50 rifles are much of a threat. But that's not going to stop the media,.