STRATFOR: "One function of the U.S. presence in Benghazi, Libya, was to help facilitate the flow of Libyan arms to Syrian rebels"

"...To date, the United States and EU countries have resisted directly arming the rebels, but covert efforts facilitate the flow of arms from other parties to the rebels have been going on for well over a year now.

One of the functions of the U.S. presence in Benghazi, Libya, was to help facilitate the flow of Libyan arms to Syrian rebels. From the American point of view, sending weapons to Syria not only helps the rebels there, but every SA-7b shoulder-fired surface-to-air missile sent to Syria to be fired at a regime helicopter or MiG fighter is one less missile that can find its way into the hands of militants in the region. Promoting the flow of weapons out of Libya to Syria also makes weapons in Libya much more expensive, and can therefore reduce the ability of local militia groups -- or regional militant groups such as al Qaeda in the Islamic Maghreb or Boko Haram -- to procure weapons from Libya.

Even though the U.S. and Turkish governments are involved in the process of passing arms from Libya to Syria, it is nonetheless a black arms channel. The Austrian Steyr Aug rifles and Swiss-made hand grenades in rebel hands were purchased by Saudi Arabia and the United Arab Emirates through legal channels but then diverted to the Syrian rebels several years later via black market channels. I have not seen any of the documentation pertaining to the Croatian weapons sold to Saudi Arabia and then channeled to the Syrian rebels via Jordan, so it is difficult to judge if they were arms sold legally to the Saudis and then diverted via an illicit gray arms transaction or if the entire transfer was clandestine and hidden in black arms channels.

Obviously, the weapons supplied by the Islamic State of Iraq to Jabhat al-Nusra and other jihadist rebel groups is another case of black arms transfers. But some rebel groups have purchased weapons with cash on the black market in Lebanon and Turkey while other rebel groups have even purchased weapons from corrupt officials in the Syrian regime. Of course, the rebels have also captured some sizable arms depots from the government.... 

 It may be years before the symphony is over in Syria, but rest assured that shortly after its final crescendo, economic forces will work to ensure that the durable and fungible weapons from this theater of war begin to make their way to the next global hotspot."