Gaza Disengagement Terms in which you will find the following statement (both articles of which Hamas has violated and the PA has not held up their end of the agreement):

"ARTICLE XVIII: PREVENTION OF HOSTILE ACTS
Both sides shall take all measures necessary in order to prevent acts of terrorism, crime and hostilities directed against each other, against individuals falling under the other’s authority and against their property, and shall take legal measures against offenders. In addition, the Palestinian side shall take all measures necessary to prevent such hostile acts directed against the Settlements, the infrastructure serving them and the Military Installation Area, and the Israeli side shall take all measures necessary to prevent such hostile acts emanating from the Settlements and directed against Palestinians."

"ARTICLE XIX: MISSING PERSONS
The Palestinian Authority shall cooperate with Israel by providing all necessary assistance in the conduct of searches by Israel within the Gaza Strip and the Jericho Area for missing Israelis, as well as by providing information about missing Israelis. Israel shall cooperate with the Palestinian Authority in searching for, and providing necessary information about, missing Palestinians."