Tiny rebel group? Hamas is the government of Gaza. They took 251 hostages and held them in hospitals, schools, private homes, and humanitarian zones.
Those who committed these actions need to be held accountable. The action of taking hostages (in violation of IHL); the action of holding those hostages in protected places (in violation of the LoAC); the action of failing to provide for those hostages (in violation of IHL); the actions of failing to make armed militia distinct from the civilian population (in violation of LoAC); the actions of placing military objectives in protected places (in violation of LoAC); the actions of preventing civilian evacuation (violation of LoAC).
The remedy is for those committing these violations is to stop committing them! If they do not voluntarily stop committing these violations, then Israel has the right to use of force as an act of self-defense.