Details of the agreement mark the first time Hamas has tacitly endorsed a two-state solution to the Israeli-Palestinian conflict, if not explicitly the Jewish state's right to exist. Hamas and Fatah announced a tentative agreement several months ago, but it was never officially signed because of the tumult of an Israeli offensive in the Gaza Strip following the June 25 capture of Israeli Cpl. Gilad Shalit by gunmen from Hamas's military wing.This is certainly good news, but it is not yet reason to celebrate or re-open the money faucets. The appropriate metric of Palestinian willingness to participate in the negotiated peace process is not whether Hamas is able to share power, but whether the Palestinian government as a whole is willing and (more or less) able to crack down on extra-governmental militias. As Lebanon learned the hard way, a government cannot function if it does not enjoy a monopoly of violence within its own borders. For far too long, both Fatah and Hamas have been unwilling to subordinate their own militias and fighters to the central government. Each has been unwilling to disarm the fighters of rival groups. Thus, even when one party is negotating in good faith, it cannot control what the other groups are doing, giving small militia groups an effective veto over the negotiations.
If the Palestinian government is to be regarded as legitimate and resume receiving international aid, it must move towards unifying the various armed groups operating in the West Bank and Gaza. This is not to say that it must be capable to preventing any and all armed attacks against Israel. However, the government cannot continue to extend one hand in peace while pretending not to know the other hand is throwing a bomb. Israel and the US should immediately work with the new unity government to develop clear metrics and guidelines to determine how successful the Palestinians are at gaining control of their fractured society and political operators.