The UN is trying to create an international treaty to control the sale of small arms. Most of these weapons are of Russian design (although manufactured by several countries, mainly Russia and China). The most common weapon is the AK-47 (and its many variants). "Small arms" include machine-guns of 7.62mm, and smaller, caliber, as well as pistols and machine pistols. The international trade in small arms is estimated at $4 billion a year, and about a quarter of that is illegal. It's believed that two thirds, or more, of the combat deaths each year are from small arms. This is particularly true in wars employing many irregular troops. Traditional tribal conflicts in Africa and Asia have become a lot more bloody because of the proliferation of small arms, usually illegally obtained ones.
The treaty would impose more regulations on legitimate small arms sales, and encourage more vigorous prosecution of illegal arms traders. The treaty, like the existing one banning the use of anti-personnel mines, would largely be symbolic, a feel-good measure for those pushing it.
The reality is that the current proliferation of small arms is largely a result of the end of the Cold War. The former communist countries found themselves with millions of AK-47s and light machine-guns that they no longer needed. Communist countries were police states with very large armies and police forces. Most of these personnel were armed with AK-47s, although the majority of the troops were reservists. So their weapons spent most of the time locked up in armories. Since the 1990s, these armories were either looted (as in Albania and Iraq), or had their contents sold off, by corrupt officials, in illegal arms deals. China still manufactures a lot of AK-47s, and is willing to sell them to shady dealers. The AK-47s have flooded Africa, Asia and the Middle East in the last fifteen years, making them very cheap (less than $100).
The major gunrunners are known, but manage to find sanctuary in Eastern Europe and Russia. Another major source of such weapons are corrupt officials, who sell off weapons to anyone. Such corrupt officials also sell older weapons, instead of following orders and destroying them. A new international treaty would not stop the gun runners or corrupt officials. In practice, the key to slowing the trade in small arms is local action. This is much more difficult than enacting a new arms control treaty. Such treaties are nothing new. For most of the last thousand years, the Roman Catholic church has periodically tried to ban some weapons, and warfare in general. But weapons control, like politics, is all about local situations. There is no easy solution.