The Palestinian Authority said it arrested Sa'adat, whom the Israelis have blamed in the planning of the assassination of an Israeli Cabinet member in November.
Also at issue is the proposed inclusion of traditional adat, or unwritten laws at the village level, in a sprawling archipelagic nation of 240 million people where local mores can vary widely.
The Al Aqsa Martyrs Brigades has called for renewed attacks on Israel in retaliation for the death this week of popular Fatah leader Raed Karmi and the arrest of Ahmad Sa'adat, secretary-general of the Popular Front for the Liberation of Palestine.