Police should only use physical force to the extent necessary to secure compliance with the law or restore order when the exercise of persuasion, advice and the warning proves insufficient to reach the police. goals; and the police should use only the minimum degree of physical force necessary on a particular occasion to achieve a police objective” (Champion, 2001). Contradictory to Peel's Sixth Principle, the Broken Windows Theory was considered zero tolerance due to the harshness of the idea that out-of-control teenagers and anyone disrupting societal life would be punished, i.e. numerous crimes. “Patrol officers could be encouraged to travel to and from their duty station on public transportation and, when on the bus or subway, to enforce rules regarding smoking, drinking alcohol, disorderly behavior, etc. Enforcement of the law requires nothing other than the expulsion of the offender” (Kelling, 1997). However, in Kellin and Cole's Fixing Broken Windows, they explained that it was up to the discretion of the police officer to resolve the problem (Kelling, 1997). This is why foot patrol was such an important aspect of broken windows.