On Tue, 31 Jul 2012 23:58:27 -0700 (PDT), Doug
wrote:

the police are allowed to create crimes as they go along

This really is a problem.

How can the police be allowed to create the crime of "Cycling
northbound over a London bridge", and then punish an infringement by
detaining overnight and withholding the primary means of transport
home.

It leaves the police acting as lawmaker, prosecutor, judge, jury,
prison guard and "executioner".