Step 1: Israel invades Lebanon with the aim of destroying Hezbollah.
Step 2: The US, Israel's sponsor, calls for the "full implementation of the relevant provisions of the Taif Accords and of resolutions 1559 (2004) and 1680 (2006) that require the disarmament of all armed groups in Lebanon, so that, pursuant to the Lebanese cabinet decision of July 27, 2006, there will be no weapons or authority in Lebanon other than that of the Lebanese state."
Reality standing in the way: Israel, with its bombing campaign, has basically made Lebanon ungovernable. Maybe the IDF thinks it has good reasons for doing so; nevertheless, that is the reality on the ground. If there were "no weapons or authority in Lebanon other than that of the Lebanese state," tomorrow, there would be no weapons or authority in Lebanon, period. Israel (or Syria, if Israel flinched) could just walk in and take over.
Does anyone really imagine that Hezbollah will unilaterally disarm with only the hope that the UN will make good on the resolution's promise that it will "consider further assistance in the future to contribute to the reconstruction and development of Lebanon"? Remember, Israel has not retracted its promise to "destroy Hezbollah."
Seems pretty unlikely to me.
It also seems to me that if Israel can't or won't "destroy Hezbollah" through military force, having vowed to do so, that it's not going to get permission from Hezbollah to do so through a US-sponsored "peace treaty." See billmon for further enjoyable punditry.