Policing is the enforcement of the system of laws of a space. The police are the individuals the government of the space has authorized to carry-out policing in the space. In other words, the police has two fundamental responsibilities: to ensure that the laws of a space under its jurisdiction are obeyed and to bring those who break the laws to courts of law where guilt and punishment are determined.
Consider countries X and Y. X has its system of laws and Y has its system of laws according to their respective selective freedom. X can not police the activities inside Y and Y can not police the activities inside X unless there is a policing agreement between X and Y. The United Nations and the Interpol are examples of bodies established to provide a forum for establishing and implementing international policing agreements.
Somethings can not be successfully policed. For example, the pursuit of knowledge can not be successfully policed. The journey can only be delayed. Any group with sufficiently strong curiosity and will to know that which is of interest to them, will consistently seek to know until the knowledge is acquired or until they are no more. Thereafter, sooner or later, there will always be another group that will continue the journey. There are many examples in history of failed policing of the pursuit of knowledge.
Political leaders must know the difference between the pursuit and acquisition of knowledge and the evil use of acquired knowledge. In the context of modern international warfare, political spaces are suicidal only as a last resort after they have been existentially cornered with no way out.