I thought of the legitimation of state power a lot in the last weeks.
One strong point is that the police works under the law. And when they do not behave according to the law a court has to possibility to bring them to the court and into prison for their illegal acts as anyone else too.
A just police corp always ever react, since all citizen need to be seen as innocent until there is proof against it. This means Police legitimized by human rights can never act preventive.
And when we already know that someone needs to have the most power. Why shouldn't it be legitimized by democratic rules?