Black Market Weapons in Iraq

I found this article about black market weapons in Iraq, published in 2006. It outlines how members of the Iraqi Army and police are selling their US issued weapons on the black market, where prices have been rising steadily. According to the article, one could easily buy a Glock or Kalashnikov in the back of grocery stores or in the back of a car trunk. 

It seems like the black market for weapons in Iraq is not very hidden or secretive. The article states that these weapons are "semi-hidden" in market places. If the practice is well known, and there is evidence that these weapons are coming from the US, through the Iraqi Army and police, why isn't the US halting its practice of supplying Iraqi security with weapons?

Obviously, an abundance of weapons in the hands of Iraqi civilians is not beneficial to the US, or the Iraqis. If it is as clear as it seems in the article, it is almost as if the US is arming Iraqi civilians. While tighter restrictions on weapon sales may help ebb the black market weapons wave, it appears that the most prudent solution would be for the US to stop supplying the Iraqi Army with weapons. While many of the weapons could have been stolen from fallen soldiers after raids, the article mentions that many of the guns were unused. This indicated that Iraqi military could have immediately turned their weapons into the market. If it is clear the American-supplied weapons are found in large quantities in the black market, why is the US continuing to supply them? Because this article is three years old, it is possible that the US has changed their practice. But if it hasn't, what factors would compel them to continue to supply guns to the Iraqi army and police?