Congressmember Barbara Lee, who opposes American military intervention in Syria, believes that Congressional approval is a prerequisite to such intervention.
In advocating this view, the Congressmember is making it harder for America to advance our interest in deterring the use of chemical weapons.
Although I believe that the Congressmember is wrong on the merits of intervening in Syria, I think she is 100% right in requiring Congressional approval as a prerequisite to doing so.
One fundamental reason I believe that Congressmember Lee is correct is that if, ultimately, the administration cannot convince a majority of Congress that the administration has a plan for military action that will advance American interests at an acceptable cost, there is a very good chance that the proposed plan will have costs that are too high, will fail to achieve its goals or is otherwise not well thought out. In other words, if the administration's plan can't stand up to the heat of a Congressional debate it is very unlikely to stand up in the heat of battle.
Particularly in this case, where the way in which the administration's proposed military actions will achieve American goals is unclear, I think passing the test of Congressional approval is an essential sanity check. It will also force the administration to answer some key questions, in particular whether this is a one time strike or the possible beginning of more sustained and extensive military action, especially if Assad uses chemical weapons again.
Without getting too deeply into the Constitutional question, I would note that while there is a level of military action the President may take without Congressional authorization, military actions have the potential to escalate beyond that level and it is wiser to have the country fully on board before initiating action than having to seek such approval afterwards.
I also think it is better for American democracy if this decision is made by a body which, with all its flaws, is closer to the people and more representative of it than any single person can be.
Congress has authorized the use of military force in the past when it was convinced doing so was in America's interest. If the administration clearly articulates its goals and plans there is no reason to expect Congress not to approve the use of force again. On the other hand, Congressional disapproval it is likely to occur only if the administration fails to articulate a clear strategy and rationale for intervening, in which case we are better off if the administration goes going back to the drawing board instead of off to attack Syria.