By Win Without War coalition member Peace Action West.
Arms transferred to “moderate” rebel groups have wound up with ISIS
It has been documented that ISIS has captured U.S.-manufactured weapons in both Syria and Iraq — and they are using them on the battlefield. Advocates for arming the rebels hold out hope that improved “transparency and accountability measures” will ensure U.S. weapons and other support are not misused. But it’s quite naïve to think bureaucratic rules will hold sway over the fighters once they return to the heat of battle.
In fact, “moderate” rebels have acknowledged sharing weapons with al-Qaeda-linked forces to gain ground against Assad. As Mark Kukis pointed out in Time: “By definition rebel groups do not answer to authority. They tend to take whatever arms, training and funding they can get from friendly governments and pursue their own agenda.” In Afghanistan, with tens of thousands of US troops, weapons have fallen into the hands of the Taliban. With far fewer U.S. minders in Syria transfers could be rampant.
U.S.-backed forces have fought with or even defected to al-Qaeda and ISIS
By far, the number one objective of the Syrian rebels is to fight against the Assad regime. The fighters have local city-based, as well as ideological loyalties that will trump financial support. Therefore “moderates” have been willing to fight alongside the al-Nusra Front (the al Qaeda affiliate). Earlier this year Jamal Maarouf, the leader of the “moderate” Syrian Revolutionary Front said “’I am not fighting against al-Qaeda… it’s not our problem”.
There have also been reports of rebel fighters, including command leadership, defecting to the al-Nusra Front (i.e. al-Qaeda). Entire units have reportedly defected to ISIS. The amendment before Congress can proscribe funding for jihadist groups like al-Nusra and Ahrar al-Sham but, once fighters are on the battlefield, aspirations expressed in D.C. won’t control the fighters’ behavior.
The initial $500 million would grow to cover more fighters. The plan would also likely necessitate U.S. air cover with its associated costs.
The initial $500 million is very likely to grow. Many supporters of arming the “moderate” rebels are calling for a much wider program since the initial 2300-3000 fighters is a relatively small force. Some supporters foresee a program of several billion dollars a year for arms and training and another up to $22 billion a year for U.S. air support. With airstrikes come at least some U.S. boots on the ground in Syria for targeting etc.  All these costs could, combined with the effort in Iraq, do serious harm to the U.S. economy.
The U.S. could be dragged into an unlawful, preventative war in Syria.
All of this adds up to a “preventative war” in Syria to combat a force that is still not an imminent threat to Americans at home.  A military campaign including airstrikes would undermine the international norm against using military force inside other states. This is problematic given that the preventive war is being driven by what some counterterrorism experts describe as threat inflation or “members of the cabinet and top military officers … describing the threat in lurid terms that are not justified.”