The problem with Syria is as follows.
(This is not meant to be an exhaustive list.)
US problems:
Syria has been a thorn in our foot. It helps support Hezbollah, is closely allied with Iran, and is an everpresent threat to Israel, our ally.
Obama drew an imaginary line, and now needs to back it up. (He now says that he did not draw the line, it was congress through a bill that was passed and then signed by Bush II, but Obama did draw the line last year in an interview as well.)
Even under Obama the US is the policeman of the world. If the US stops policing no one else will, and will set precedence for further inaction.
Democrats, like Kerry have long sought peace and understanding with Assad, as seen with Kerry’s frequent ( ok, maybe not frequent, but there were at least five) dinners and drinks with Assad.
Congress passed the Syria Accountability and Lebanese Sovereignty Restoration Act (SALSRA) in 2003 that said that the US would do all it could to limit WMDs from Syria and to protect Lebanon from Syria and Hezbollah .
International problems:
Only a few countries publicly believe that Assad’s regime was the responsible party.
France has been on a war footing lately, with Libya, and now Syria. France seems to be coming out of its slumber that started after World War I, so having them as allies does not make our cause just.
The Security Council will not approve any action against Syria, Russia and China either do not believe Assad was behind the attack, or just does not see the problem.
Putin wants to see the proof.
German intelligence shows that a leader of Hezbollah called Iran and said that Assad did it. That would not even stand up as evidence in a US court, can you say hearsay?
Rebels have tried to get chemical weapons into Syria through Turkey.
Other reports of chemical weapons, beyond the most current, point at both the rebels and the regime.
Syria is not a signatory of the chemical weapons ban treaty. A country can only be held responsible for what it has agreed to, otherwise it’s anarchy. As Peter Venkman said in Ghostbusters, it’s “Human sacrifice! Dogs and cats, living together! Mass hysteria!”
The use of SALSRA as a reason for war is shaky, because this is an internal matter, and no other nation has been threatened or attacked with chemical weapons. Beyond that one state can not make another states actions illegal, it just is not possible with international law. US law stops at our borders, plain and simple.
There is nothing, but imperialism that would show that Obama had a right to start a war with the Assad regime.