This editorial says what i've been wanting to say about Syria without me really knowing the specific relevant laws and treaties. My version is "It is illegal to use chemical weapons, but it's also illegal to bomb another country without UN sanction".

The editorial's version:

Syria is a party to neither the Biological Weapons Convention of 1972 nor the Chemical Weapons Convention of 1993, and even if it were, the treaties rely on the United Nations Security Council to enforce them -- a major flaw. Syria is a party to the Geneva Protocol, a 1925 treaty that bans the use of toxic gases in wars. But this treaty was designed after World War I with international war in mind, not internal conflicts.

...

Arguably, the key legal obligation of nations in the post-1945 world is adherence to the United Nations Charter. It demands that states refrain "from the threat or use of force against the territorial integrity or political independence of any state." The use of force is permitted when authorized by the Security Council or for self-defense (and countries like Jordan and Turkey are considering this route to justify joining an anti-Assad coalition) -- but not purely on humanitarian grounds.

This is in contrast to my Senator, whose statement says:

The mass atrocity committed by the Assad regime in grave violation of international law is searing to the soul and blinding to the eye. To allow a despot to gas their population indiscriminately and with impunity is to fail our values and to compromise our freedoms. There is no fork in the road before us, there is no ambiguity to the evidence, for the use of chemical weapons against the innocent brings us to a point of no return. The Syrian regime and others like it must understand that red lines are indelible, that our foes should never question the resolve of the United States.

I love the pivot to "our foes". Syria is in the midst of a civil war. One side (allegedly) used chemical weapons against the other side. And that is in violation of an international norm, and the attack also killed civilians, and that is absolutely deplorable. But how does that make anyone "our foes" or "compromise our freedoms"?

The editorial's author Ian Hurd goes on to say that he supports attacking Syria on the grounds that it is "illegal but legitimate" from a moral perspective (i'm simplifying his more nuanced and legalistic opinion a bit so please don't rely on my summary).

I don't agree with Hurd's conclusion. There are sadly a lot of atrocities in the word and the US can't solve them and certainly can't solve them by just dropping bombs (per this article that i've linked to previously, if we really want to solve a problem here militarily we have to commit to boots on the ground, something i also don't support and something the administration is equivocating on). So that removes the moral component here. It's ugly but the fact remains that we can't solve Syria's problems with missiles. So that leaves the legal argument that Syria broke the law and we (not the UN; we) have to respond. But Hurd's editorial shows the problem there. So i don't think there's a strong case to be made in favor of bombing Syria.

So here's to hoping again that the resolution in Congress fails. It's seeming more and more likely to pass. Pelosi is supporting it, Boehner is supporting it, my senator is writing the damn bill (and he was just re-elected in 2012 so he's not worried about voters). And i really hate that my allies on this are the opportunistic Tea Party Republicans that are reflexively anti-Obama and anything he supports. But i'm hoping there's enough outpouring of regular voters against this - latest poll shows 60% against - to stop it.