This is incorrect. In 1992, the PLO had little military presence and were exiled abroad. The West Bank was governed by Israel. The Oslo Accords allowed the PLO to return and govern their people, including the establishment and expansion of their security forces.
They had little "declared" presence. But obviously, as anyone can tell you, the Palestinian militant movements are very guerilla and very grassroots, and renouncing violence in order to govern and have "security forces" while their enemies did not promise any such thing is not an improvement.
The most obvious proof of this is the intifiada which followed Oslo
