That the PA has little "enforcement capabilities" is logic. Never in history a resistance group against an occupation has laid down weapons before an end to occupation had taken place or was in sight. Take IRA etc. Should Olmert and Abbas have agreed on a time schedule for Israeli withdrawel from the West Bank, things would have been different. At this moment there is no end to occupation in sight, so logic that the resistance will keep weapons and certainly not give them to Abbas who is seen as an Israeli servant anyway.
Abbas to urge UN to pressure Israel to permit entrance to Palestinian refugees from Syria (Haaretz)
from the article: In the West Bank, wanted militants are made to feel unwanted