This paper deals with the tension that appears between on the one hand laws and rules which try to control police activities, police efficiency and police fairness, and on the other hand police discretion, regarded as essential by police officers on the beat. It also underlines the need for flexibility that every police officer has to use in order to preserve or to improve his relationship with the citizens. Because people have complex demands, because they don't want the police officer to apply the rules without any discretion, what would be undearable, negotiation has to be part of the police officer's job. But the pilling up of new rules is restraining this flexibility.