As some of you may know, I have long argued that humanitarian intervention is morally and legally permissible (see here). I stand by those arguments, and that is why I firmly believe that we should not intervene in Syria. I have several reasons, but two are prominent.
1) A justified intervention must be on behalf of those who have a just cause. In Syria, the available evidence shows that neither side has a just cause. The government is your standard Middle Eastern oppressor, while the rebels are dominated by Al Qaeda and similar sinister characters.
2) It is unjust for our government to tax American citizens to try to help people who do not want to be helped and who, even after they have been helped, instead of thanking us for liberating them, they viciously turn against us for domestic political gain or some other spurious motive. Iraq and Afghanistan are cases in point. The U.S. and their allies helped them get rid of their tyrants, only to see the new governments posture about how bad Americans are. When this happens, our response should be simple and direct: we will leave you alone to lead your miserable lives. And if you dare attack us, we will kill you or bring you to justice.