Here we go again. Read the Constitution---there are only two uses of the military permitted: 1. to repel invasions; 2. to quell insurrections. To get around that, Presidents have been relying on the War Powers Act to use our military pretty much whenever they see fit. The trouble is...laws do NOT supercede the Constitution. Using our military as the world's police force, no matter how justified, is unconstitutional. There is no legitimate authority for that use. Yes, what's happening in Syria is an obscenity, but that has nothing whatsoever to do with constitutional use of the military.
An Amendment is required to change the situation, but politicians just pass laws instead. [It's easier to do that than to get 3/4ths of the States to ratify a new Amendment.] That's called "Legislative Absolutism", a term coined by Justice Harlan in 1901; it means passing laws with no regard for the limitations placed upon the Feds by the Constitution.
Let's not forget that Hitler, Mussolini, Stalin, Pinochet, & others all had "laws" in place to justify their actions, too. The Constitution is the Supreme Law of the Land. Change it if you must, but do not simply ignore it. Changing it must be done by amendment or a constitutional convention; no other ways are permitted in our system of government. None.
As always...just my opinion...after ~ 50 years of serious study of the U.S. Constitution, probably the most plainly written document ever put forth by a government.