If we were at war, you might have a point. As it stands, Congress has not declared war on anyone. Are you sure? A declaration of war has no set formula per the constitution or statute. It is an up or down vote (which has already taken place) and we could argue that authorization to use force is fundamentally the same thing.
And even if they did, how would we find the enemy? They are not a nation-state, as they would be under the conventional definition of warfare. They are shadowy, international organizations composed of individuals who disappear into the civilian population. Conventional military force is usless against them, unless you find a remote headquarters or training facility. Even then, conventional forces are not the best option. I need to acquaint you with some friends of mine. Conventional forces are working quite well in Iraq, and apparently Lebanon as well.
As recent events in England have shown us, good intel and solid police work can do more to roll up terror networks than force of arms. Actually, no one "rolled up" a network. At best they got a cell or two. Your statement would be more accurate to say that under certain conditions law enforcement can be as effective as the military. Terrorism is, and has been, largely the provenance of law enforcement. Thus terrorist activities are best prosecuted under civil-law. Your logic doesn't work. "Thus terrorist" doesn't flow from "largely the provenance". The use of methods such as extreme rendition, torture, and information acquired under duress do more harm than good to any case the government can bring to such courts. We must either live up to American ideals, or live down to those of the terrorists. Unfortunately for America and the world, Chimpy and Co. have chosen the latter route. Y'all are really lucky I wasn't the President. You'd have never heard of half the terrorists. Catch em, drug em, question them, drain them, shoot them (in that order).