The global arms trade isn't simply about increasing violence or defense or good business or whatever one might immediately think it's about. It's also about political control. Poor countries with unstable governments will often sell off rights to national resources to buy arms and consolidate their power. This not only further oppresses the people of the country in question, but also further impoverishes them since ownership of resources is transferred out of the country and domestic revenues are taken from other potential projects.
People in the development organization world often talk about this as corruption on the part of political rulers of the purchasing country. But it's also a case of moral corruption and political opportunism on the part of arms selling countries. The major ones are, of course, the US, China, Russia, France, Germany, and the UK, all of whom - except for France and Germany - have either voted against (solely the US) or abstained from joining any new arms trade agreement. The US and Russia, in particular, sell massive amounts of arms to developing countries. Sales from the US have increased post-9-11, including to human rights violators. France and others, by comparison, sell largely to industrialized countries. (See here for who buys and who sells). In the US, the industry is heavily subsidized (this means that we citizens fund the trade). (For more information, see the FAS' Arms Sales Monitoring Project).
On the other hand, this statement strikes me as absurd:
(One of the development practitioners calling for a halt to the trade is the economist / philosopher Amartya Sen. See this June 2006 opinion piece in the IHT).
The UK ambassador for disarmament at the UN, John Duncan, said the vote was "a great success".
"We have 139 nations which have said: 'Yes, we want a responsible arms trade and we're prepared to discuss it in the UN, with both the consumers and the producers,'" he said.