International law recognizes that a police force may constitute a legitimate military target when it is part of the armed forces.
There is evidence that an overwhelming majority of the police forces were also members of the Hamas military wing or activists of Hamas or other terrorist organizations.
Hamas’s internal security services are terrorist operatives, armed with a variety of heavy weapons with standing orders to fight Israeli forces. Under the Law of Armed Conflict, Israel is permitted to target such forces and their bases of operation.
Extended Answer