You know, things are different in theory and in practice. You see, even in the US, there are numerous laws and court cases that limit the power of police. But when it comes to practice, US police can shoot down everyone that who resist their order without bearing any legal responsibility. In other words, what the law say simply carries no practical effect.
What I mean is that the police is given enough autonomous power and they are free to manage their internal business. The autonomy of police is much much greater than any other government departments. The law already gives sufficient protection to the police. It' not correct to say that the police are not protected for the execution of their duty.