It's been how long Israel pounding and invading lebanon? Why there are still Hezballah and Katyushas?
If Israel wanted to it could completly wipe Lebonon off the map. It is trying not to kill civilians in a war where they are fighting an enemy which hides behind civilians.
If Syria actually used its Army, Not guerrilla fighters and attacked Israel, that would mean a real country vs. country war, and Israel would spare no thought in sending back to Syria what they intend to do to Israel.
Big difference when your fighting terrorists, and when your fighting an actual countries.
I am sure you are aware of the hundreds upon thousands of Jericho III Nuclear Bombs Israel holds in its Negev Silo's that could effectivly wipe out the whole Middle East. Hopefully Syria isn't foolish enough to actually attack Israel, and the world will be spared a Nuclear War.